Getting Over An Ex Help?

so me and this girl back two years and its no question i've never loved anybody more than her. we liked eachother when we fisrt started getting to know one another but didnt date cuz she had a bf at the time. we stayed friends, i fell for her and awhile later we had a huge fight which we stopped talking for 6 months. one night she came up to me and apologized for everything and we became friends again. a week after i realized i still had feelings for her. this time around she was single but really involved in school and a few months later she started to act really weird and awkward toward me which led to me getting frustrated to the point where i just snapped. i was sick of being mistreated by her and even after i snapped all our friends actually took my side. they said shes bi - polar, crazy forget about her etc. so i did, the past few months we act professional at work around one another but that's it. the thing is, is that i don't want her anymore. i'd be an absolute tool if i even forgave her again for what she had done. the way i see it, she already blew her 2nd chance. i even look at her now and am like yeah i really don't even see her like that anymore either. at the same time though i miss her. and even thinking back to things like of her with someone else kinda bothers me. not where im like jealous but i dont even know its confusing. i never really got a real answer as to why she started acting the way she did toward me and have been debating for weeks about writing her a letter just letting her know how i feel. ive constantly been dreaming about her alot too. it feels like yeah im ready to move on, i dont want to be with her, but im having trouble completely letting go. perhaps its just i dont want to let go of the feeling of being in love with her. so yeah any advice at all with that would be appreciated