Did my girlfriend cheat on me? should i blame her?

WE got into a fight over the phone and we were talking about a break where we wouldnt date other people. So we hung up and she started crying really hard and another dude (her friend) came up hugged her. She was telling him how much she loves me and she said she knew it was a break but she took it like a break up emotionally. she said she was really emotional and deep in thought wishing i was there. while she cried then propped her head up and kissed her for 2 seconds (she puckered by reaction she said) then tried to put in tongue after 3 seconds and she backed off cuz the taste of cigs. she said she was compltely emotoinal and shocked and confused and it took her that long to react..she said she was vulernable.She said she never expected someone to kiss her while she talked about how much she loved me.but she feels awful for the stupid situation she put herself in and that it happened. her brother said he had never seen her cry that hard in her life that day..even though she said she was crying like 7 out of 10 when it actually happened in terms of how bad she was crying..cuz the dude calmed her down a little.she swears to god about this and she is a really good person...i just dont understand how it could take you that long to react? she said it wasnt the boy it could of been anyone. she also says its cuz i wasnt thier to make up and she wishes i was there and the dude just happened to be thier for her..she thinks thats why it happened.she orignally blamed herself and thought she cheated because she accepted it but then as we talked she told me she really didnt knowingly accept it and was scrambled..she said she didnt really know how to clify the situation cuz it has never happenened before....but ive never been that vulernable..is this plausable? did she cheat or no?