<human>: I've been seeing my girlfriend for about a month now and I'm already pretty much head-over-heels for her. She's beautiful, super fun to be around, we have loads in common and we just connected like on another level. It's been over a year since I've been in a relationship because I just haven't felt that spark with anyone, but I felt it almost immediately with her.  

Everything is great besides one problem: her ex-girlfriend. They got an apartment together and have a lease for another year. I was fine with this at first because they aren't together, just friends, and I figured everything would okay. I'm not really a very jealous person. But the first time I stayed over, ex-girlfriend started acting crazy. She would send my girlfriend texts that hinted that she was going to kill herself, texted her constantly all day and blew her phone up if she didn't reply quickly enough, etc. She ended up writing "once a whore, you're nothing more" on the bathroom mirror for me to wake up to after hearing us having sex the night before. She gets angry whenever my girlfriend spends time with me and is very passive aggressive. She's obviously very jealous and isn't over her relationship with my girlfriend.  

My girlfriend is stuck there because of her lease. I understand that and I wouldn't ask for her to break it. However, she also wants to stay best friends with this girl, who has been acting awful to me and who is clearly still interested in her. My girlfriend gets upset whenever I express any dislike towards the ex and she defends her up and down when I bring up anything negative that she's done. I've tried to explain that I'm just not comfortable with the two of them being so close after the way that the ex has acted, but she says I'm being unreasonable and unfair to her.

I really like my girlfriend and I don't want to break up with her. How should I handle this situation? Is it even worth trying to figure things out?

Give me the gist of the text in a nutshell
<bot>: My girlfriend lives and is best friends her ex, who is still in love with her and who has been very hostile towards me. How to navigate the situation?