Should we let my step daughter talk to her mom?

Back story:

Husband found out of the blue that he had a 6 year old daughter that was being put up for adoption by the state because the mother was found with meth in her system while being pregnant with her 6th child (at 25 years old!). She has custody of none! She lost total rights of my step daughter as well. All taken by state. In our state, CPS will not just take your kids away unless you really mess up. They will give you hundreds of opportunities before they do something drastic as taking your parental rights. Luckily the mom reached out to us on time, and my step daughter found her dad.

She's 8 now and every time she gets in trouble she runs to her room and cries for her mom. Something she never did. She has not lived with her mother since the age of 5.

We know who she is. We can easily find her on Facebook. Do you guys think is a good idea to let her have contact with her mom or should we keep her away and let her look for her on her own time when she's an adult?

If we're keeping her away it's because we think it's for her own good. We only want the best. Her recent claim for her mom has me wondering if we're doing the right thing.

What would you guys do?