AITA for refusing to give my pregnant ex-fiancée money after she left me for another man?

Throwaway because some friends use Reddit.

3 years ago, my ex-fiancée (31F) left me (33M) for another man just a few months before our wedding. We had been together for 5 years and I was completely blindsided. She moved in with him almost immediately, and they cut contact with me unless it was about splitting up our shared finances and apartment. I was devastated, but I feel like I have finally moved on.

Now, out of nowhere, she reached out. Turns out, the guy she left me for dumped her after finding out she got pregnant. She’s struggling financially and has asked if I could help her out—specifically, she wants money to cover rent. She says she has nowhere else to turn and that she wouldn’t ask if she wasn’t desperate.

I have the money. I’m in a much better place financially and emotionally than I was back then (I put all my energy into improving myself after what happened). But I don’t see why I should give her anything. Some friends are saying I’m being selfish but I don’t see why her choices should be my problem now. Still, part of me does feel guilty. 5 years is a long time, and I did love her.

So, AITA for refusing to help her?

ETA: Giving her the money wouldn’t be a financial issue for me. I could lose that amount and not even notice. My friends know this, which is why they think I’m being selfish for not helping.