Girlfriend knowingly dated a guy with girlfriend?

[Anonymous]

Title says it all, kinda makes me worried if she might be one to condone cheating..
They dated 8 month, but the guy was promising to leave his girlfriend the whole time... I don't know if that changes things.
Any perspective is welcomed.

[Anonymous]

Red flag unless you want an open relationship. Since she is okay with you dating other women while with her, she is most likely willing to date other guys while with you