I feel like I'm at the end of my rope. Most of the time things are good with my Mom. But sometimes she gets in severely depressed and angry moods. When she does she says some very extremely hurtful things. Things like how she regrets having me as a daughter, how useless I am, etc. Within a day or two she gets better and things go back to normal. I know that it's her depression and frustration talking, but her words take their toll. It especially hurts as I stayed to take care of her while my brother and sister took off the first chance they got. I try to do my best by her, but it gets hard as I have severe depression and anxiety.
People say things that they don’t mean when they are going through difficulties. It’s up to us to tell them that we aren’t going to listen to it. Walk away if needed. You aren’t obligated to listen to her abuse.
Don’t hesitate to speak with her about other living arrangements.
For the 'useless' stab, respond with - not sure why you would say that. I am quite useful to you. I clean/bathe/etc/etc for you each and every day. Do you know anyone else that is more useful to you? I would like an apology and for you not to say that again. If you would be happier somewhere else, please let me know. Your words are hurtful.
If she is clear headed and aware of what she is saying, she needs to be called out on it. If she has no idea what she's saying or dementia related, you may just have to come up with some lighthearted reply: Why, yesterday you told me I was your favorite child. Or, 10 minutes ago you thanked me for being so helpful.
Mother can HIRE in home caregivers or move into Assisted Living where she pays others to put up with her caustic personality. A daughter does not deserve to be treated like dirt. She either stops the crap or faces the consequences, her choice.
Good luck!
If moving out of the house isn't an option then completely ignore her when the abusive behavior starts up. The next time she calls you useless, let her experience firsthand what real useless is like.
Do absolutely nothing for her. Do not lift a finger. If she calls for you and needs or wants something, totally ignore her. Go and stay somewhere with a friend or something for a few days if you have to. Don't take her calls either. Tell your siblings or another family member where you are and that you're staying there and not taking mom's calls for a few days.
Mom needs a little tough love and has to learn that words have power and abusive behavior has consequences. This is what I did and it works.
I have to say, I think your siblings are correct to keep their distance from your mother given how she chooses to behave. (You don’t mention dementia or other cognitive issues that would cause her to lash out without knowing what she is saying.)
Have you considered taking steps to remove yourself from this situation?