"" "" But she's discovering she just may not be a drop bar kind of rider - she doesn't like the position, it bothers her palms and thumbs, and she finds modern brifters just too uncomfortable for small hands."" ""

Does mean any place on the bars? or does she not like riding in the 'drops'? I seldom ride in the drops unless I am headed down hill. I think a fitting is in order to be sure the fit is right and remember other than the saddle/knee/crank relation few fit rules are hard and fast. She does not have to bent over and stretched out like a pro racer in a time trial. I get lots of ribbing over in the C&V section for my tall stems but they make riding more comfortable for me.

As mentioned maybe the pace is not comfortable for he. maybe she needs to ride more and the group take it easy on her now and then. Being constantly dropped by a group, especially friends, can be very discouraging.