Am I selfish for not wanting my SD to visit with BM

So I will start off by getting it out of the way that SD7 and I don't have a very good relationship, which is my fault but therapy didn't help it after like 2 years, and my husband does have primary custody so SD is with us the vast majority of the time. I really do want what's best for SD at the end of the day but there is a lot of banked up frustration. I've also asked a lot of people for advice and got a lot of really conflicting answers, varying from "you're her real mom and need to go all in on being her mom" to "you should nacho." So I have tried different things and they have all gotten jumbled up and it feels like a mess that I am trying very hard to fix. Therapy didn't work but I'm reading all the parenting books and trying to incorporate the advice. But while I struggle with the day-to-day, I have always wanted what is best for SD and never wanted her to like, suffer unnecessarily.

Anyway, SD has also not seen her mom since like Thanksgiving, allegedly due to financial issues and needing her car fixed. She also stopped calling SD because she did not want to have to answer "I don't know" when SD asked when she could see her.

BM just got her tax return and is now wanting to use that money to see SD. I know it's not my decision but I don't want her to go and told my husband as much. Here are my reasons why:

1. BM wants to jump straight into an overnight visit and refuses to see SD for 1 or 2 daytime visits and start calling consistently again before this happens.

2. I'm not sure about the reliability of BM's car and she lives 1.5 hours away.

3. BM has a new boyfriend SD has never met and I know Jack Squat about him. Literally just a first name. And although nothing suspicious has ever come up about him, it's just an unknown and I know how predators will try to date single moms in order to gain access to their kids.

4. (and this is where I think I might be selfish) I am 9 months pregnant and SD and I's relationship is so rocky. SD has also been having some emotional issues lately, this is probably in part due to her mom's absence, in part due to the new baby coming, and in part probably due to me just not handling things very well. BM's bank accounts are also about to be frozen due to a debt she neglected to pay, so I doubt she will be able to see her for more than one weekend. I don't want SD to see her mom and have it stir up all those feelings and then have the baby come less than a month later. I feel that this would be super hard on SD and of course I don't want that. But I also feel like the behaviors that are going to come along with those emotions are going to be very difficult on our family. I am already worried about how I will handle the postpartum stage mental health wise, and having a kid act out and have an attitude with me when I'm sleep deprived and hormonal... I worry it will be too much for me. In addition to also being too hard on her.

I am really looking for support here and no negativity or judgement. I feel like I genuinely can't look at this objectively. Am I just being selfish here, or would it actually be in SD's best interest to go see her mom for like one time before the baby comes (and then probably not for months again after that)?