Not sure what to do either, if anything.
According to DS (who lies non-stop so there's really no knowing the truth) he looked her up on FB. He said it was because he's bored during lockdown. He claims that they have only exchanged a few messages, but he won't let me see any of the messages.
DS is nearly 16 so still not adult, he's also quite troubled, struggling at school and often in trouble with the law. He hears what he wants to hear and is easily manipulated (although not by us, he is very uncooperative at home).
BM appears to have turned her life around, she was not at all in a position to care for a child when DS was born and he was removed at birth. I've had a look at her FB page and she has a primary aged child and has become religious. She is also in direct contact with DS's older half-sibling who is an adult. Although she hasn't posted on FB for over a year so I don't know whether that is still the case.
I'm not even sure how worried to be. I didn't meet her but she was always described as a very nice person, if lacking in the ability to make wise choices. Much like DS is probably. But really I don't know her, and as I said, I don't know what sort of messages have been exchanged. We are in different countries so there's no chance of them arranging to meet, certainly not at the moment anyway during lockdown.