How can I get my wife up when she falls?

You make a call to your 911 service and ask for a "Lift Assist" when the paramedics arrive they will help her up and gt her back into her chair or bed. As long as there is no transport to the hospital there normally is no charge for a Lift Assist. (I called for 9 Lift Assists over the course of 3 years never was charged, and the paramedics were amazing!)
This is the safest way, they are trained to lift a person safely so there would be no injury to her or to you.
When I called I would do the following:
Make sure my Husband was safe, not going to fall more, put a pillow under his head..
Call 911
Turn on the porch light
Put a note on the door that it was open and the dogs were confined.
I would confine the dogs.
I would return to my Husband and make sure he was comfortable and not frightened.
When the paramedics arrived they would walk in and I would call out that I was in ...whatever room we were in.
They would ask if I wanted transport to the hospital, I would say no and they would have me sign papers stating I was declining transport.
Then they would be on their way. Takes minutes.

I found a video on youtube posted by Occupational Therapist Rhonda B which shows ideas on how to use common items in your home to get up from a fall. It is called "How to get up from the floor (after a fall) - MacGyver style!" You can find it at:
https://www.youtube.com/watch?v=4ETgQD8QhZs
I like the fact that it gives you a visual, I believe that makes it easier to follow.

In the beginning, one of us, my sister or myself, drove to the fire department and asked if there was someone available to help us get our mother up and one of volunteers came to help us. They told us to just call 911 in the future and they would call them to come. We were hesitant to do that if it wasn't an actual emergency but they assured us it was OK. When we had a few actual emergencies and she needed to go to the hospital, the fire department always came anyway and were the first ones there, so I guess this is part of what they do.

You might want to check with the local fire department in your area and see what they suggest before the next time it happens, then you will know for sure.

all fire departments in this country provide “lift assists” for people who have fallen. All you have to do is call 911 and request one. They will send the fire dept out to lift the fallen person. At your age I would not try to lift dead weight.

My daughter is an RN and this is how she picked up Mom when she fell in the shower.

Daughter spread her legs apart in line with her shoulders. Then she bent her knees going as low as she needed to get to Moms sitting position. She instructed Mom to put her arms around daughters neck. Then my daughter wrapped her arms around Mom just under her arms. Using her legs, not her back, she lifted Mom to a standing position. Then walked her out of the shower onto the toilet which was right there.

Kbuser's suggestion is really good. Start with a stool and then a chair. Less strain on ur legs. My daughter is short. A taller person should have more leverage.

When my father began falling (luckily not hurting himself), I had to call 911. I felt terrible to have to do this but there was no one available to help me. That was when i decided I could no longer care for him at home, sadly. But this time, fortunately, his dementia had reached the point that he wasn't aware he was no longer living in his home. But this repeated falling was a sign to me that it was time for him to move to where there were people who could safely help him up from the floor. Good luck.

Not much mention of avoiding falls.

Falls are very serious in the elderly. I worked with actuarial data for my career. Once an elderly person starts to fall due to physical reasons, the mortality rate in that population is 50% within 2 years. Complications from broken bones and head injuries are some of the biggest causes of death and disability.

Given that, preventing falls is key. Assisted living facilities are assessed and graded on how many falls their patients have. In our state, if an AL resident falls more than X number of times in 6 months, the state regulations are they cannot stay in AL, they are nursing home status.

I'd get an assessment by an MD for any elder who has repeated falls. The MD can suggest a care plan to avoid the falls, which may include a referral to physical therapy. home modifications, etc.

Here in Las Vegas we have a non-emergency number to call for such assistance. No charge but very helpful. they told me it is part of what I pay for in their service. Paramedics come with the engine and checked her out.
Saved my back.
she and I also worked out the use of furniture to get her up. The easiest was to get her near the couch and help her to roll up onto it then she could sit up.
A visiting nurse provided lot of help in all of this.
Then there is still the old chair lift thing. If you have a strong back and a sturdy chair.

You call 911 and tell them she's not hurt (if she isn't) but can't get her up. They will come and lift her up for you. Had to do that many times with my mom and also with myself. They know how to pick her up without hurting her and it will save you from getting hurt too.

These techniques only work with someone who is uninjured, of reasonable weight and still has the leg strength and cognitive ability to assist you in getting them to their feet. My mother had nerve impairment in one leg and would have simple falls every 6-12 months for decades. Often she could get to her feet herself using the chair technique and I only had to carry the chair to her fall site. When she became older and less able to help I almost always got help for the stool technique. If you have any doubts about your wife's ability to assist or your own strength, please ask for help from neighbors or a lift assist from a local fire department or EMTs. In my area, the fire department bills your insurance or asks for a donation; they do not want cost to be a factor when a senior needs a little help.

One technique that works with someone who has difficulty getting up but still has enough strength to push to stand is to use a chair. The person who has fallen gets onto their hand and knees (you may need to place a pillow under the knees if this position is painful). The assistant places a sturdy arm chair in front of the person and assists the fallen person to rising enough to place their hands and then their forearms on the chair's seat, pushing the chair toward the fallen as needed while making sure it does not slide away from the fallen person at any time. Using the chair for leverage, the fallen pushes up to their feet and then stands using the chair arms for leverage and balance. Often the fallen then turns around and takes a seat.

Another method requires you or you and a friend be able to lift the person a few inches onto a solid low stool. Place the stool as close as possible behind the fallen person. Place your forearm under the person's shoulder - do not grab their arm with your hand. While you are lifting from one side and hopefully another person is lifting from the other side while the fallen pushes as much from their legs as possible, you set the person on the low stool. I could often then place my feet in front of the fallen's feet and lean back pulling her to her feet using our grasped forearms. Two people (one on each side) can lift a person from the stool. A stronger person can stand behind the fallen person with their arms clasped under the fallen's shoulders and hands clasped together across the fallen's chest while lifting the fallen onto the stool.

When doing any lifting, please remember to keep your back as straight as possible and use your legs for most of the lifting power.