I feel you, man.
My mom is great, mind you. My challenge is my adult daughter. I do have the (very large!) advantage over you of already being established. Well enough that from an actual financial perspective I can probably weather just about anything she can do. But the emotional situation is similar, with the twist that as her father I feel like I actually AM responsible.
I'm in the process of preparing to screw myself to help her go to beauty school, so that she hopefully ends up with some way to support herself. I just paid off $3K of debt that collectors were hounding her for, so that she can get a student loan for another $12K -- which I'm co-signing. Without that debt paid off the bank wouldn't lend her money even with a solid co-signer. With it paid off, they'll lend to her but only if I'm on the hook. To sort of put her on the hook for the $3K she owes me, I took out a signature loan with her as co-signer. The understanding is that I'll make the payments on both loans until she graduates and starts earning an income, then she'll pick them up.
Here's what's really going to happen: She'll go to school for a while and then get in a fight with one of her classmates or instructors and announce that everyone there hates her and that she can't do it any more and refuses to go. Of course, the school insists on getting paid up front. There is a refund schedule if you don't finish, on a sliding scale depending on how far you got before you quit, but the schedule starts with them keeping 50% of the $10K tuition and all of the $2K materials costs, that's if you quit the first day. It rapidly gets worse after that. I don't blame the school; I'm sure they need to protect themselves.
So, then, she'll have $15K of loans which my name is on, and be unable to pay them. So either I'll make the payments or my credit rating will go down the toilet. Which means I'll make the payments. But even though that's how I expect it to go down, I'm going to do it anyway, because there is a chance that she may actually be able to do this and I really want to help her get herself established. She does really like doing hair, nails and makeup, so maybe.
Anyway, I'm posting this mostly as an exercise in mutual self-pity and to reassure you that you're not alone (as if you didn't know that), but I also have some concrete suggestions for you.
First, I think you should decide which is more important to you, the $2K your mom owes you, or the relationship you have with her. I'm not implying that you should decide one way or the other, mind you, that's totally on you, and deciding against the relationship wouldn't be unreasonable. But if you decide that the relationship is more important, you should let the money go. It's poisoning the relationship, and it'll get worse.
Second, in the future if she needs money, and you want to give it to her, make it a gift. If you can't do that, you might consider the bank loan idea, as I'm doing with my daughter. It doesn't change the fact that you may end up eating the loss, but it changes the relationship. Rather than you demanding that she give you money, the bank is demanding that both of you give them money, and both of you know it's really her responsibility and that by making her payment you're bailing her out. Each payment you make is a gift to her... but at least they're smaller, more manageable gifts.
I'm setting up automatic payments with my bank's bill pay feature, and using their "confirmation" feature to send my daughter both an e-mail and a text about each and every payment I make for her, ostensibly to keep her in the loop because it's her debt, but really to remind her of each gift.
Third, you may consider using the phone as leverage. It's yours, and you're allowing her to use it. When you've had it and just can't take any more of some particular thing, tell her that if she doesn't cut it out, you'll turn the phone off. This is a fairly effective tool with my daughter, but your mom may be less dependent on the phone. At least with my service provider (Verizon) I can easily suspend and resume service on any line on my account.
Fourth, and most important, I'll tell you what many of my daughter's therapists have told me: Take care of yourself first. They compare it to the airplane safety video, where you're told that if the oxygen masks drop you shut put your own on first, before trying to help anyone else, because if you don't take care of yourself first it's possible both you and the person you would have helped may die. The same principle applies... and beyond taking care of her, you owe yourself a decent life.
Take care, seriously.