To Accept or Not... That is the ?

I'm an adoptive mother and I've got two daughters and two very different adoptions. My first DD was adopted from DFS (Kinship placement) Basically our best friends grown daughter had all 6 of her children taken and we have adopted 1 of them. So we've seen first mom grow up from a kid, so we're attached to her in an "niece" sort of way. Our best friends are still "grandparents" we'll just explain it to DD when it comes up lol. But first mom has all sorts of issues, SERIOUS mental health problems(clinically dx), drugs problems both Rx & Non (unless you live in IL now :P), bad relationships, very unstable and has never really gotten it together & just unfortunately unable to take care of her kiddos. Even with support. She's sent me several friend requests on Facebook and I just haven't accepted it. I'm going to put out there as well that my second DD's first mom is my friend on Facebook we talk and share and dote on our shared kiddo. She's a safe, secure, positive and beyond all a generally good person, she is a teen but she's a remarkable young lady. I can honestly say I love my kiddo's first moms, both of them. My 1st DD's is just a bit different than the 2nd's. Just not sure how to handle it. That's not to say that I don't share with her we do send pics, texts and I beg her for more contact with DD. She's pulled away (protecting her heart I suppose) not us... but this is a level of closeness I share with my 2nd DD's first mom. I'm also just not sure I want her to see the relationship I have with 2nd DD's first mom either (to protect her feelings & to avoid the attempt to have the same). As it's not safe for my 1st DD for me to have that kind of relationship with her first mom. Just looking for support and ideas from those who have faced this as adoptive parents. I realize my situation is a bit unique seeing as though both of my children were brought in to my life because of my close relationships with my friends; but I'm assuming other people have adopted more than once and this issue has come up. Thanks again!