So she wanted a baby with a man she thought was a responsible father and good husband
Then when the baby was conceived she found out he was none of those things
If she sign the Birth Certificate it makes her morally and financially and emotionally responsible, which is what he wants, especially the financial part.
I don't think she is wrong for not claiming the baby (by signing the B'Cert), because in her heart she probably really wanted the baby, she most likely does not want any part of it because she now see it as a scam on Sally's part to hit her up financially.
She probably feels used and hurt because she was emotionally involved with this....Yes, I'll say it thief, scammer, bum and any other low life descriptive word I cam imagine.
Listen to your Lawyers girl, because once you sign on the dotted line you are in it for 18 yrs, at least.