Not sure what to title this

We've been foster parents for years, however, we are taking in my niece in a week or two and we'll be doing guardianship for her. Her mom (my Step-SIL) has been in prison since 2010. Even though she thinks she is getting out "any day" the reality is she may be in prison until 2016. My father in law has been her guardian since mom went into prison, but he currently doesn't feel able to handle her, and feels like she needs more of a traditional family dynamic. There are several other reasons for the move, but it boils down to resources, they have none and we have enough. Well, of course because of the legal process involved in guardianship, bio mom was notified and now has our phone number and has called 8 times in the last 2 days. I did accept 2 of the calls and she assures me she is not going to contest the guardianship modification (she's glad actually). However, she believes that she is getting out any day and then Niece will go live with her. I want to keep her involved, we understand from our time as FPs how important that connection can be, but the reality is I can't afford to talk to her as often as she is calling. Niece has been in guardianship for 18m, and at 2y we are allowed to file for TPR and adoption in my state...and that's our plan. SIL is nice when she's not using drugs, but she has 7 other kids spread across the US that she's not parenting because of her drug use and time in various prisons (honestly, I'm not sure how she's able to have kids, she must get knocked up each time she's released) so her ability to stay clean is a concern. I've seen too many kids go back to questionable situations, and to be honest, it seems like TPR hasn't been done because my husband's family is lazy. Anyway, I guess I'm just looking to connect with other people who are caring for kin, but not because CPS got involved.