ive always thought that
I honestly would do some research on the potential
butch and try to find out what she is (sexually). If she is a lesbian, she may very well be trying to coup d'état your marriage.
Make sure that that's the case though. Don't let a jealousy episode play with your mind and possibly ruin your relationship.
For all it's worth... I had a similar experience with a male neighbor and him flirting with my wife... weirdest experience in many years. The dude would walk by me and not say a thing, then walk to my wife and start a conversation. Every. Fucking. Time. It was so weird that even his wife noticed the strange behavior. Anyhow, I had a talk with his wife and she must've chewed his ear off because the flirting came to an end rather quickly. They've since moved on to another town, but boy oh boy, talk about weird and uncomfortable.