Dementia?

DO: (short explanation) “Hi Mom. You look wonderful! This is Eric. We work together.”
“Who are you? Where’s my husband?”
Don’t: (take it personally) “What do you mean – who’s your husband?” I am!”
DO: (go with the flow, reassure) “He’ll be here for dinner.”
(distract) “How about some milk and cookies?… Would you like chocolate chip or oatmeal?”
“I’m going to the store for a newspaper.”
Don’t: (repeat differently) “Please put your shoes on.”…You’ll need to put your shoes on.”
DO: (repeat exactly) “Please put your shoes on.”… “Please put your shoes on.”
“I don’t want to eat this! I hate chicken.”
Don’t: (respond negatively) “You just told me you wanted chicken. I’m not making you anything else, so you better eat it!”
Do: (accept blame) “I’m so sorry, I forgot. I was in such a rush that it slipped my mind.
(respond positively) Let me see what else we have available.” Leave the room and try again.
Need support? We’re here to help! Speak with one of our dementia experts by calling 858.492.4400 or emailing info@alzsd.org.

Sounds like your mother is displaying the typical behaviors of dementia/Alzheimer's. My mother has never had much compassion or empathy, but now with dementia, it's ZERO. She's only concerned with herself and has no regard for anyone else's feelings at all. She argues vehemently, too, and will contradict herself in an effort to continue arguing.

If your mother is suffering from dementia, she's probably reluctant to get diagnosed out of fear. If you can get her to the doctor for a cognitive exam, that would be great. In the meantime, here is a short list of do's and don'ts for dealing with dementia sufferers:

Do’s and Don’ts of Communication and Dementia

You can’t control memory loss – only your reaction to it.
For people with dementia, their disability is memory loss. Asking them to remember is like asking a blind person to read. (Common questions like “Did you take your pills?” or “What did you do today?” are the equivalent of asking them to remember something.) A loss of this magnitude reduces the capacity to reason. Expecting them to be reasonable or to accept your conclusion is unrealistic. Don’t correct, contradict, blame or insist. Reminders are rarely kind. They tell a person how disabled they are – over and over again.
People living with dementia say and do normal things for someone with memory impairment. If they were deliberately trying to exasperate you, they would have a different diagnosis. Forgive them…always. For example, your wife isn’t purposely hiding your favorite pair of shoes. She thinks she’s protecting them by putting them in a safe place…and then forgets.
Here are some basic Do’s when it comes to communication with someone with dementia:
Give short, one sentence explanations.
Allow plenty of time for comprehension, and then triple it.
Repeat instructions or sentences exactly the same way.
Avoid insistence. Try again later.
Agree with them or distract them to a different subject or activity.
Accept the blame when something’s wrong (even if it’s fantasy).
Leave the room, if necessary, to avoid confrontations.
Respond to the feelings rather than the words.
Be patient and cheerful and reassuring. Do go with the flow.
Practice 100% forgiveness. Memory loss progresses daily.
Here are some Don’ts:
Don’t reason.
Don’t argue.
Don’t confront.
Don’t remind them they forget.
Don’t question recent memory.
Don’t take it personally.
We’ve put together some specific examples of good and bad communication below, keeping these do’s and don’ts in mind.
“What doctor’s appointment? There’s nothing wrong with me.”
Don’t: (reason) “You’ve been seeing the doctor every three months for the last two years. It’s written on the calendar and I told you about it yesterday and this morning.”
DO: (short explanation) “It’s just a regular checkup.”
(accept blame) “I’m sorry if I forgot to tell you.”
“I didn’t write this check for $500. Someone at the bank is forging my signature.”
Don’t: (argue) “What? Don’t be silly! The bank wouldn’t be forging your signature.”
DO: (respond to feelings) “That’s a scary thought.”
(reassure) “I’ll make sure they don’t do that.”
(distract) “Would you help me fold the towels?”
“Nobody’s going to make decisions for me. You can go now…and don’t come back!”
Don’t: (confront) “I’m not going anywhere and you can’t remember enough to make your own decisions.”
DO: (accept blame or respond to feelings) “I’m sorry this is a tough time.”
(reassure) “I love you and we’re going to get through this together.”
(distract) “You know what? Don has a new job. He’s really excited about it.”
“Joe hasn’t called for a long time. I hope he’s okay.”
Don’t: (remind) “Joe called yesterday and you talked with him for 15 minutes.”
DO: (reassure) “You really like talking with him don’t you?”
(distract) “Let’s call him when we get back from our walk.”
“Hello, Mary. I see you’ve brought a friend with you.”
Don’t: (question memory) “Hi Mom. You remember Eric, don’t you? What did you do today?”

Continued.........................

This could be anything from UTI (probably not for 6 months but they can reoccur)
Medication change and or reaction with another medication.
A "mini" stroke or series of them. This could also be the start of Vascular Dementia.
The first thing is to get her to see a doctor so an accurate diagnosis can be made.
Prior to this past 6 months have you notices any other "odd" things...think back 1, 2, 3 years not just the past months.