Ex is making my life living hell

21M been dealing with a ongoing battle with my ex for close to 5 months

Back in January I split with my ex fiance of 5 years it's a long story but a short breakdown:

I found videos on her phone of her cheating back in October she did the whole "it was a one time thing it'll never happen again" stuff and I fell for it, it killed me but I persevered and kept trying, eventually atemped to split with her in December because I couldn't handle it and she somehow still manupulated me into staying, in January I moved into a new house with her and 2 friends and a week later I found ongoing messages with her talking to the same guy, turns out they had been meeting up every other night for what you can assume, that night she just up and left without saying anything after I mentioned it but from there it's been a struggle, rents unaffordable now but I'm making do.

The now tough situation that reappeared after 4 months:

When we moved into this house our flatemates loaned us money for the bond till we got the bond money back from our old house, I paid mine asap but she only ended up sending 1/4 of the money for some unknown reason (we made her sign a form stating she'd pay because we knew she'd be shady but she's still refusing)

she signed up to study at the same college as me recently and harasses me daily, she was a graffiti artist when we were together and she's used this to tag up my neighborhood around my house to constantly remind me of her.

It's just been to long, any moment I get of peace just gets shut down by something she does and I'm getting tired of it, I want nothing more than to move on