I think the facebook thing is a heart breaker. I am never on facebook so its not an issue, I don't think you need to unfriend her just change your settings so that her feed does not show up on your page.
The mutual friend thing stings, Its happening to me as well but with the inlaws. They were my family and now I am an outsider.
Hopefully with your GAL you can meet new people? I haven't made new friends that way yet, but its a start
Me late 30's W mid 30's T 15, M 10 S4, S7 ILYBNILWY June 2015 In house S July 2015 W rings off Oct 2015 My ring off Feb 2015 Separate houses June 2016