Decisions

So I was dating this guy who claimed be was madly in love me with.. During one of his stay overs I found out he was dating another girl this whole time.. When I asked him he said he wasn't.. We fought he continued to maintain his innocence until finally he stopped replying to me and it ended. Now my question is do I text this girl to let her know what was happening.. He was snapchating her while I was laying in his lap and texting her i miss you when he was in my bed. Is it worth reaching out... And yes I may be coming from a vengeful place but I want opinions

UPDATE : I did it. She said she's glad I reached out and that it's over with him and wants to hangout lol. 😀