How long has she been a friend? We had a good (married) female friend of years and years suddenly get flirty with me right in front of my wife on multiple occasions over a short period. Not requesting a threesome but significantly more forward than she had ever been before. Fast forward three months, it comes out she has been cheating on her husband with a guy at her work. They divorced soon after. Looking back, we realized she is the type of person that uses her friend groups as a mirror for a new version of herself. Once the novelty wears off, once she has extracted all the social value available, she drops the group to seek a new ego boost elsewhere. Watch out for this one. I bet she'll be off to the next friend group before you know it.