I feel guilty about swearing to my ex gf

So my ex broke up with it’s been a while like a year or so . But she’s held a grudge against me for swearing to her and saying to her new bf she’s a Sl*t .

I said this in anger because I found out she was talking to this new guy before fully breaking up with me instead of breaking up Honestly she lied and said she doesn’t want any relationship at the moment but soon after break up she was with someone else so it’s most likely she was talking to him while with me. Anyways later on I told her bf I just said that in anger and that she’s a nice girl but she still hates me lol