Friend can't stop lying

hi, my problem is slightly different maybe a bit weird. so i have known this boy for over five years online. our families know each other now after we eventually met. he had a girlfriend who didn't know of my existence. my boyfriends knew of him. he couldn't go seconds without talking to me though - because i tink he can't be alone. long story short..we were very thick! he is a funny guy. last year i introduced him to a girl i just befriended thinking they shared the same sense of humour. the girl started to lie to me and said they weren't chatting. i don't know why she did that but she did. and then every time i had a fall out with either they would immediately be online together. this happened so many times that it was hard to ignore. also stuff i'd say to him miraculously fell from her mouth. i confronted him recently. he denied outright but wanted to sort out our issues as we have not been talking properly for a year which is weird for both of us. now i realise that he has gone and told her this because she's blocked me online and has changed her dp to 'fcuk this shit'. am imaginging things? it is not hard to come to this conclusion though because i was a secret in his life for his gf and she has plenty t o hide from her fiancee. they both are programmed to be secretive. i know i am not going to talk to him ever properly. but i need some advice to take my mind off it.

when i say boyfriends i mean i broke up twice recently. also, i understand they might be venting to each other but i wanted him to be honest about it as he doesn't know her and this girl is mean to me..and why would he do this from several miles away? by the way he is in a different country!