My Ex (26F) broke up with me (29M) two weeks ago. Now she wants me back.

Me and my ex were in a relationship for almost 3 years (supposed to be my 3rd anniversary tommorow). We're working together in the creative industry. Everything was fine and we were obsessed about each other until 2 months ago. For work related, I met this guy (25M), who's an expert musician and we instantly became friends. I have a helping mentality, he was going through some depression and I lifted him up, took him to therapy and I even introduced him tp my gf. They instantly clicked and became good buddies and at first it was kind of a brother sister vibe. I was so happy for them as they both were finding it difficult to make friends and I was grateful I could help. We stayed at his place and later we invited him to her place and we had a lot fun together at first. Eventually she started acting different towards me, like I could know the slightest difference in attachment. At first it was minute, then it became more and more evident. Her calls started getting fewer and she started acting disinterested in me. I constantly communicated with her about how I was feeling and she assured me everything was fine. Up until one day I logged into her IG (I knew the password), and I saw her sending DMS (not sexting) and memes to the new guy and she was leaving my messages on unread. As days passed she became more and more distant. Then they started making plans, and she invited him over as let me know about it in the last minute. One of mutual friend (21 guy) also joined them and these 3 became a gang. These 3 went on a stay over for some days and for the first time I decided to stop making the effort. Not to my surprise she didn't make much effort to contact me and we didn't talk for almost a week in our relationship. Then came my birthday, she came again with this guy and the rest of my friends to surprise me, 2 days after that she broke up with me. I have had enough at this point and i said okay. For the next 10 days we didn't contact, and we met for work on the 11th day. She was constantly trying to grab my attention, and she asked me to talk with me in private. She said she missed me so much, and she needed a hug. She said I was the best boyfriend ever. I explicitly said I've accepted the reality and we're not meant to be together and we need to move on. She got really shattered in hearing that and showed she had tattooed 'irreplaceable ' on her body as a reminder of me. I said she deserve better and I walked away. From that day we been meeting for work and she's been trying to grab my attention, crying etc. She's been saying 'you can come cuddle with me anytime' and we can be FWB etc etc…she's totally lost and devastated. I checked her DMS once again, and though they were very close and communicating, there was no sexting going on..I'm now totally confused and seeing her this broken makes me kind of sad. Should I give her another chance, as I don't want to regret losing her once she's moved on..?

Ps: she jumped from next to next in her previous relationships, except those guys went after the breakup and in my case, I was the one who walked away.