You are not self aware!
Read what you wrote..
"I did set boundaries" - "she wouldn't fucking leave" - you didn't set boundaries, she used to crossing your boundaries so you have no idea how to set boundaries with her!!! What you did it's not called setting boundaries!
"I mentioned to her that her presence made my GF uncomfortable" - why did you say something stupid like that?? Why use your girlfriend as excuse? That's why she doesn't trust you, you are a weak person! You need to say to your girlfriend "I don't want you..." "I'll call cops..." I'll get restrictive order.." YOU don't want her and if she still do something, you do what you said you'll do! That's setting boundaries, that's how she'll take you seriously!
"she said she was sorry" - wow how nice of her.. SHE IS NOT SORRY!!! She wants you to fix.. who cares what she wants? You know what she wants, she wants to ruin you, ruin your relationship, she'll blame you for everything, keep blaming you, you'll give her everything, keep giving... It will never stop until you understand your stupidity!!!
Seriously your new girlfriend should just leave, not waste a second anymore with someone like you.
Know your self worth!!! Know what you want and stop doing it for others but do it for yourself!!!!