Female- don't eff crazy and these 2 ladies are battling it out over you and getting a bit weird. Don't date D's friend's mom. D needs her stable relationships and if things go south with you and the mom, it'll hurt your girl. If they go well, your W will try to drive a wedge between them. Please let bff mom know this. It's a gentle, kind thing - flirty is cool and she is attractive, but you don't want to make life any more complicated for the girls.
Faith is, at one and the same time, absolutely necessary and altogether impossible. --Stanislaw Lem