Did my wife cheat, of was it my fault? cont'd?

(stupid computer) Did i help this, i know i did in a way but i never thought she'd do that, i know the guy very well and i know he would try s@#$ like that but i would never believe she would let him. She has many excuses as for way she did it like wanted to see what it felt like which doesn't make me feel better, and caught up in the moment. Any way please any answer will help either i'm an idiot or she is or we both are. Please, please, im hurting and need to hear someone else's opinion