I don't mean to be disrespectful, Bella, but if your mom had her own home, why in the WORLD are YOU getting the dunning letters?????
They should NOT be contacting YOU. Nor sending any communications TO you.
I personally, would write "No such person" or "person unknown" on the letters and send'em back. Really, I know that you're worried about your mom and I understand that you want to be apprised of everything that's going on. But realistically, unless you're prepared to pay all the delinquent bills and take over the mortgage payments, there's really NOTHING you CAN do.
All you're doing is stressing out over something that can't be helped or changed (by you). Your mom has made clear that she's not going to pay and doesn't really care. So, really, you shouldn't either.
I don't mean to sound all "Tough Love" on you, but really, you're just leaving yourself open to unnecessary stress and aggravation. And since you're currently working on YOUR credit ills, you can't afford to voluntarily adopt someone else's woes. At least, not until you've solved your own problems.
But let's go further. Let's say that you HAVE fixed your credit and you're sitting pretty at NO baddies, and a nice 850 FICO:
What CAN you do? Can you pay ALL of her bills? I doubt that. Mortgages ain't cheap. If it was, she'd be able to pay it.
Can you file BK for her? Nope.
Can you act as legal representation on her behalf? Nope (unless there's a law degree you didn't mention).
ALL you CAN do is advise her. And even then, all you can do is advise her to pay her bills. Which, I'm sure you've done.
Beyond giving her advice, there's nothing you CAN do. You've given her the benefit of your wisdom, you've given her options. It's up to HER to decide what to do. And since you said that she said she ain't paying. That's her decision.
You've done ALL you CAN. You're done. You can listen to her, commiserate with her, maybe even pursue a few options for her IF she ASKS (such as DVing, HIPAAing, etc), but that's IT.
The rest is just, honestly, crap you can't do a durn thing about.