Cheating?

Apparently flirting with a guy who you want to fuck isn't cheating. My gf of 6 years recently broke up with me. She had a bunch of excuses but when I brought up her cheating by flirting with this guy she met online for over a year, she claimed it wasn't cheating. She later admitted that she wanted to fuck him. But, said it still wasn't cheating because he is engaged to get married and she told him not to flirt with her because he had a gf. She never said to not flirt with her because she has a bf. He doesn't even know me. I walked in on her one time taking nude pics while she was messaging him. She later sent those pics to me after she was done talking to him. She acts like im an idiot who doesn't know what is going on. She eventually took a break from texting me last night to call me, crying because I called her a gold digger and cheater, because that is what she is. 6 years of a relationship down the drain because she's too lazy to work, keep the house clean, or even to take care of the children properly. I just needed to get that out.