When Meri Lin was trying to parent her daughter, she frequently justified keeping her away from other people (even family) partially because she understood the physical danger involved in being around her child. Do you think Theresa has considered this and has accepted that her children might be in danger if she takes Ivy into her home? Or do you think she hasn't really thought it through? Knowing Theresa, if Ivy DID hurt one of her kids, do you think she'd stand for it or do you think she'd kick Ivy out?
I'm pretty sure The Resa has considered the dangers of trying to raise baby Amanda. She doesn't seem like a very impulsive woman and I could've sworn she alluded to Mennie about the difficulties and dangers of a "special needs" child like Amanda. I think she sees how Mennie interacts with Amanda and has considered that with her own children (do we know how old and what sexes The Resa's kids are?) and fully intends to have Mennie be somewhat of a part of the new blended family she's planning.
I'm really not sure if Amanda is capable of hurting someone yet. I mean I know she has the power, but it seems like even in her tantrums (or better, when Mennie smacked her) she hasn't yet seriously harmed anyone. I'm hoping it's instinctive like the way most cared for, large family dogs have a gentleness about them around the children of the family and just know to back off as soon as someone says "OW!" Though I guess Amanda's power potentially could go from strong to lethal faster than an "OW" could be produced.
Sweeping all of that aside, I think as long as The resa's kids aren't seriously injured AND if the kids aren't permanently afraid of Amanda that she will try her best to hold it all together beyond any incident. However, even if one of those things does happen, I still don't believe she is the type that could just abandoned Amanda to the wild. I think that The Resa would try harder than anything to find some place safe for Amanda to be before she let her go, some place with more apt caregivers and that she'd still come and see Amanda as often as possible. Guilt alone would see to that, but heart would guarantee it.