Advice on boyfriend's newly outed lesbian daughter being excluded from sleepovers with other girls...

Advice for both the grown-ups in this 11yo's life, and also for her. We did expect some parents not to want her to do sleepovers with their children anymore, but tonight a long-time friend said he wouldn't want a straight boy having a sleepover with his daughters, and probably same for her, because sex stuff might happen with the girls. I'm pretty upset over it, the child doesn't know this came up, and I'm not even sure how I can tell her dad without ruining the friendship between the families. What would you do? Kill 'em with kindness? What can I do to help her be secure with her emerging choices? I don't think she ought to be somehow suspect, excluded, or shamed in any way just for owning her own preferences. Cross-posted on /r/TwoXChromosomes/ for a variety of perspectives... And boy, is there some variety... Any advice for us or for her?