Stella,
If the mutual friend keeps telling you things, it's ok to kindly but firmly say something like, thank you for telling me what you've already told me, but I don't think it's in my best interest to hear any more. I appreciate you being so honest with me. And then change the topic. There comes a point where any additional information is not helpful.

xoxoxo

M 20+ T25+
S ~15.5 (BD)
BD 4/6/15
D 12/23/16

"Someone I loved once gave me
A box full of darkness.
It took me years to understand,
That this too, was a gift."
~ Mary Oliver