Little update on the situation:

When I split from my ex, it was because I cheated with a guy from work's ex.. Well he fell out with me, then met up with my ex, then it all went silent for ages..

Now the guy from work is ok with me again and chats to me sometimes.. He text me saying that my ex text him about the prossies, and asked me if its true. I said its bullshit. He said she told him that her neighbor saw me going into a "well known ho house".

So thats her basis for this lie. Her neighbour apparantly saw me visit a well known ho house. I also know who her neighbor is.. Thought he was an alright dude in his 40s.. Prick