Advice about Siblings bonded to separate foster parents

I have a difficult situation that I'm wondering if I can get some advice on. My wife and I fostered 4 sibling girls for 9 months. The biological parents were close to losing their parental rights and DCFS asked us to sign intent to adopt. We felt a reciprocal bond with the youngest child but had no bonding in either direction with the older 3 children. However, we had an immediate family member who had been our respite providers who had gained a reciprocal bond with the older 3 girls, but no bond with the younger girl. They were willing to take the younger if DCFS didn't want to split them up, but they felt that the younger girl belonged with us. They also had 3 adopted children already and they felt that 7 total was too many. We were also concerned that the 4-year old would get ignored in such a large family (other 6 children between 9-14 and not needing as much individual attention). We approached DCFS to consider transitioning the girls to the other home and to consider whether it would be in the best interests of the children to separate them. Although it normally wouldn't seem in sibling's best interest to be split up, we lived in the same city and would be able to facilitate frequent visits. The girls had also already been split up from 3 older sisters and had not shown any signs of trouble with the separation. The girls each had their own counselor and we had a counselor to help us as parents. The counselors each wrote letters to DCFS with their assessment of the best interests of the children. We weren't given copies of the letters, but 4 of the 5 told us in person that they recommended the girls be separated. The 5th didn't tell us what her recommendation was. When we met with DCFS the Guardian ad Litem said she wasn't willing under any circumstances to consider separating the girls. The discussion ended with no pros/cons being discussed. The other foster family never expressed their concerns about the younger girl with DCFS. The decision was made by DCFS to move all 4 girls to this other family. It was frustrating to feel like the GaL had all the power even though she'd only met the girls 2x. We explained the decision to the girls that we weren't able to adopt them and that they'd be transitioning to this other home. The three older girls were ecstatic about the decision but the youngest girl was hesitant. We never discussed the idea of separation with the girls and they don't know it had ever been considered. We slowly transitioned them to the new home over 2 months by doing sleep-overs/etc. We knew it would be difficult for the youngest girl, so we made sure to talk with her frequently about her new parents and her new house/etc. They have now been fully transitioned to this other home for 2 months, so it has been a total of 4 months since the DCFS decision. The 3 oldest girls have blossomed and are so much better off than they were at our house. However, the youngest girl still cries herself to sleep every night asking for us. We see the girls on weekends at family gatherings. The 3 older girls tell us how sad the youngest is, that she wants to live with us, and that she cries for hours whenever they leave the family gatherings. The youngest girl stays by our side the entire family gathering, has no interest in interacting with the other children, tells us she wants to live with us, and cries when she has to go home. I do remember this same child crying for her biological parents every night for several months when she first came to our home. I don't remember at what exact point she transitioned to being bonded to us, it just happened. I'm hopeful the same will happen with the new family. We make every effort to talk to her about her new parents/etc whenever we see her at family gatherings. In fact, we sadly even try to avoid her a little bit, even though we don't want to, because we want to help her move on. It hurts inside to not be able to parent her, seeing her so sad, and knowing she wants it and we want it, but knowing it's out of our control. We don't show her any emotions of sadness we just explain that she has a new home now and that she'll be okay and we'll see her the next weekend. If the child continues to have a difficult time transitioning, at what point should we consider speaking with DCFS about whether the transition was the best choice and whether it makes sense to re-consider splitting the children and returning the youngest to our home? We don't want to cause any problems with the new family or with DCFS, but it is hard to feel like the wrong decision may have been made and to have no control over it. In the long-term, is it certainly better for the child to be with her siblings, or would it be in her best interests to be in a separate home with parents she is bonded to? Will she be able to bond in a few months, or will this become a long-term trauma? I think it would be important to get the new parents perspective on the situation. Sadly, we've had a difficult time discussing anything with them; they seem closed off since the girls have moved to their home, like we've offended them or something (or they're too exhausted to talk), Hopefully we'll be able to get that resolved soon. I assume that DCFS will figure out on their own that the transition is difficult, so it may not be necessary for us to bring it up. However, in the case of the new foster parents it seems to be the "elephant in the room", so maybe it will never be discussed. Any advice? Thank You.