You should embarass her by commenting under the pics "Thanks for coming to my mums funeral. I see you had a great time" I think those of her friends that aren't self centered airheads will be properly horrified.
Oh my god! I'm so sorry for your loss OP.
Personally, I probably would never speak to those fucking idiots ever again. To try and put the spotlight on themselves at your mother's funeral is just completely unacceptable. How disrespectful to not show any remorse.