AIO my bestfriend was being inappropriate with my boyfriend

So a few days ago I (22F) went out with my friend Sally (23F) and her friend Julie (22F) to get drinks at a bar. For some context Sally used to work at this bar and through her I met my current boyfriend Mark (21M), who still works there and was working that night. So other than knowing Mark through me, she was also his colleague for a few months. Sally also has a boyfriend who was not present.

That night, from the moment we got there, Sally kept flirting/having private conversations/constantly going up to other men, including my boyfriend’s colleague, who I will call James (27M). Although she has a boyfriend, this did not surprise me because she used to do the same thing when they worked together. She also spent a great portion of the night complaining to me and Julie about her boyfriend who was not there, and again this was not surprising for me because they’ve been in an unhappy realtionship for a while now.

When the bar closed, we all waited for Mark and James to be done so we could go get a drink at another bar. We started walking, and as I got caught up in a conversation with Julie, ahead of other people, I heard Sally screaming/laughing while being carried on what I thought were James’ shoulders. I turned around to see nobody behind us so I started calling Mark who did not pick up his phone. At this point I was very confused and me and Julie just looked at eachother and decided to keep walking. We turned around the corner to see Sally and Mark laughing their ass off and Sally started loudly telling me about how Mark was carrying her on his shoulders and she almost fell.

In that moment I felt like absolute shit but didn’t say anything and just asked Mark to please not leave me behind and pick up his phone the next time and we all kept walking. He noticed something was wrong so I told him and made sure nobody else heard and he just kept apologising and told me that she asked to be carried because she said her feet hurt since she was wearing heels. I know he didn’t mean any harm and was just being “friendly” towards her, but it still hurts.

I, later that night, also spoke to another friend, who knows Mark very well, and she basically just said that he probably did not realize/see her flirting with other men all night and just thought that she being friendly.

At this point I just felt very hurt so when Sally told me she was about to leave I just asked her to talk and told her that her behavior that night made me feel uncomfortable, especially with Mark. She denied everything (including flirting with other men), lied and said that Mark has asked her to jump on his shoulders, and then just started crying and talking about how she wants to break up with her boyfriend. Her friend Julie also joined the conversation and when she realized what we were talking about she told Sally that she also felt uncomfortable when we saw Mark running by and her on his shoulders.

The next day she messaged me talking about other things as if nothing happened, meanwhile I felt like shit all day and just spent the day in disbelief.

I also talked to Mark, he said in that moment he hadn’t realized it was inappropriate and just thought it was friendly banter (he jokes a lot with everyone) and that he hadn’t seen her being all over James and the others. He spent all day apologising and listening to me. I believe him because he is very clueless sometimes although it still hurts. Nothing of this kind has ever happened between us, and our relationship has always been healthy. This also happened the night before Valentine’s day which kinda ruined the day for me.

He also showed me a few texts they had exchanged because he asked her what shoe size I wear, he surprised me with the shoes I’ve been wanting to get for Valentine’s day, and when he told her that she said something along the lines of “oh god why aren’t all men like you”. She texted him again in the evening the day after all this happened to ask him if I liked the shoes (she could’ve asked me when she texted me in the morning).

I still feel like shit and wonder if I should cut her off without saying anything or confront her again now that she’s sober. Am I overreacting? I cannot stop thinking about it.

Also sorry if the grammar sucks but english is not my first language.