Help! Ex and bestfriend

Okay so I dated this dude about 3 years ago, he was my first proper boyfriend and my first love, he was AMAZING. Anyway, we still are close, however a few months after we broke up I found out my bestfriend had gone to meet him and kissed him, we fell out really bad over this but then rekindled our friendship.

A few months ago I went to a party and someone she was sleeping with told me she had been talking shit about etc and then the next day she went mad thinking I was trying to get on him which I wasn't and explained everything he had said and showed her messages and everyone that was around told her that she had got it wrong and I was only curious about what she had apparently said as multiple people have told me the same thing.

Anyway about a month ago her and my ex was always on call so obviously I was getting annoyed because why is my bestfriend always on call to my ex type of thing, he added me to the group call and straight away I said that how she was being was fake and that she wouldn't like it if I was to do that with anyone she was messing with in any sort of way. She put it on her nan's ashes that she hadn't been trying to talk to him like that and that she wouldn't want us to fall out in the past.

She knows how i feel about the whole situation and knows how I felt last time.

However today my ex has shown me pictures of her bare boobs and ass.

Advice would be appreciated. This just shows to me that she really doesn't value me or our friendship to do the same thing not once but twice.