Boyfriend & bestfriend

So my best friend has a past of getting with guys that have girlfriends.

When my boyfriend broke up with his ex my friend tried doing things with him ( she didn’t know they had broken up)

She’s sucked his penis a little but he told her to stop, this was back in January

I am now with this guy and she told me would never go near him and he doesn’t like her would never go near her, but obviously they have history together. I trust him but I’m not sure about her


I don’t really know what to think of the situation I’m in