讓她去

That means you know where he is now. My suggestion is, let her to meet him whether he's a nice guy or not. Don't let you two's past affect your daughter, no matter what, that's her dad. I know your daughter must know how hard you have been in the past, and she won't forget this at all if she is a caring and kind kid. After she meets her dad, if they like to keep in touch, that's their decision, but for sure he has to answer a lot of questions, for example why he didn't support the family.

Another thing is, if he doesn't want to meet her, then you need to let her know too so that she won't blame on you. That's very important: a lot of times, because of the past, some mom/dad blocks their kids to meet the ex, the result could be not nice to them at the very end.

Blood is blood, it could mean a lot, but sometimes it could mean nothing. Let her go and just be yourself. Sometimes fate is unfair, but at the end, it'll be fair for everyone. Whatever we sew, we will harvest later.