Have been no contact with Ex girlfriend but she keeps sending hurtful thinigs to me WHY?

Ok so I came on here nearly 2 months ago discussing my heartbreak over my recent breakup. My partner (Im 26 she's 20 btw) and I were together over 2 years and very happy. She wanted us to move out of our parents houses to be more adult and get a place of our own. This was a mive step for me in the relationship but I loved this girl and did whatever made her happy so we moved into an apartment together. After only 6 weeks the relationship was over. The 3 weeks before the split she completly changed towards me with little to no affection, starting little arguments, and wanting to constantly go out then no longer inviting me. We work at the same place and got invited to many socials, but these people work in hospitality and can drink and do drugs all the way til late morning, which I didn't like but I went once again to make my girlfriend happy. At one of these parties she started telling personal stuff about me and her to a co worker (who shes known for 6 months and they were never friends before) who later he expressed feelings towards her and told her to dump me as she is too young to know when she's found the "one". When we broke up I was a reck but she was cold and hasn't cried once being as selfish and immature as I've come to realise she is now. Since then I got great advice and dropped off the face of the earth from her. We still see each other at work and at sum parties but never make eye contact and I thought we were moving on. Then after valentines day people at work said they were pissed off at the fact that my Ex was now seeing this co worker sean after the 2 claimed they weren't. I already knew they were sleeping together but now she was diving straight into a relationship with him, which angered sympathetic staff towards me. My Ex believed i said sumthing to annoy her co workers so she sent me a message on facebook claiming to have been screwing sean all of valentines day. this hurt me a lot but i didnt want to give her a reaction so i didnt respond. then she deleted me off all networking sites and finally has started becoming friends again with her Ex before me who used to stalk and beat her!!! She claims she has never been this happy in her life and that the 2 years with me she felt constricted? She's gone from living her dream as an adult with me in a luxury apartment to jumping between sean's dads (btw sean is younger then her) place and her girl friends roach ridden house (also occupied by parents). At the start of the split she would drink heavily, do drugs, and party to wee hours in morning, she still does these things but now is doing all the so called boring stuff she did with me now with her co worker like staying in cuddling watching tv...WTF??? What I want to know is why is she still putting these things across to get my attention when me and her are doing no contact? I cant tell if she wants me to step in or say sumthing? did 2 years with me really mean nothing? how can she want to be friends with her Ex who beat her so bad and not with someone who treated her right and loved her dearly? is she lying when she says shes truly happy now? This just doesn't make any sense? Sorry guys for long post just wanted to get reactions and if anyone has had similar experiences? thanks