If a woman EVER associates with another man in any way at all, other than family... or business (this is also dangerous territory... watch out for this closely) she’s cheating. There is ZERO reason that a woman whom is your significant other should be associating with another man. If this happens... leave. You’ll see that right after... this man she claimed that was ‘just a friend’ will be the literal FIRST man she jumps onto. These are 100% facts. She usually has more than 1 as well. The funny part is if you try to explain to her that you’re completely uncomfortable with this situation, and you prefer that she doesn’t associate with this guy... you’ll be labeled as an insecure controlling person. Just leave. Let them go enjoy each other’s terrible time.