Any practical guidance for end of life support?

I’ll echo the hope that you have hospice services. We used bendy straws for my dad to drink and when he couldn’t do that anymore one nurse made the wise suggestion of making ice chips from his favorite drink. He’d eat those right off a spoon enjoying the flavor and easy to swallow

First I hope you have hospice involved if your mother is nearing end of life. They will try and help her get her pain under control, and if needed they can bring her to the hospice facility to do just that.
My husband while under their care started on morphine and that didn't help at all. They then started him on Fentanyl patches and again with not much success. They eventually put him on a Fentanyl pain pump, which initially did help quite a bit, but as his pain increased, I had him brought to the hospice facility so they could better monitor his pain. He eventually came back home still on the Fentanyl pain pump, but at the maximum dose legally allowed.
Because all narcotics do make a person constipated, I used laxatives, prune juice, suppositories, Miralax, and everything else I could think of, but as his pain medicine increased so did his constipation, and on several occasions hospice had to come and give him a shot of Relistor in his arm, which worked in a matter of about 15 minutes to clean him out.
You may want to at this point also thicken your moms drinks with the product Thick It. That will help prevent her liquids from going into her lungs and her developing aspiration pneumonia. I would put my husband thickened drinks in his thermos, and he was able to drink from that just fine.
Hospice will be covered 100% under your moms Medicare and they will supply any and all needed equipment, supplies, and medications. They will also have a nurse to come out once a week to start, and aides to come bathe her several times a week, so if you've not yet gotten them involved, please do so now.
I wish you and your mother the very best.

Yes, if on Hospice talk to the Nurse. Mom is not suppose to be in pain. If not on Hospice, then have her evaluated for the service.

Nieves, welcome to the forum. I am so sorry that you are facing losing your mom.

Is mom on Hospice? The Hospice nurses should be able to address both the issue of her untreated pain and constipation. You are wise to bring thus up; opioids like morphine are very constipating.

Do you know what the leg pain stems from? She may need a different pain med, like a muscle relaxant or nerve med like gabapentin.