What do I do in this situation?

My ex who is kinda crazy tbh is constantly constantly spread in lies about me and just bending the truth about a ton of stuff like an example is she texted me from a fake number and was telling me too off myself and cussing my out and just being shitty in general and the next day she told evryone I was the one who texted her and that u told her to kill herself which is quite literally the opposite of what happened but thats just an example of what she’s done (there’s a lot of stuff thats happened) but I have no idea how but we became friends (I didn’t really want to be friends she kinda forced it) but my friend Tyler was at my house and he said we should call her and they were flirting and both of them kept on making fun of me to get each others attention with at one point my ex making fun of my insecurities to make Tyler laugh but they got each others numbers and are now dating but before that my ex told Tyler that I was saying bad things about him when I never said anything bad about him oh yeah also my ex broke up with her boyfriend to get with Tyler but anyways Tyler instantly aimed she was telling the truth and I warned Tyler about her being a bad person and he said “I hate you your just jealous you asshole” I don’t know what to do can I have some help?