I find that when my boyfriend does it as a slow caress, it feels really good. sometimes when you rub the area with more than a little pressure, it can become a little uncomfortable because that specific area is pretty sensitve and the skin is a lot thinner. its especially uncomfortable if you focus on the same spot. since your girlfriend doesn't like it.. try caressing her inner thighs lighty with your fingertips while kissing her. maybe that will do the trick
even though you weren't asking for advice, hopefully that will work for you if you really wanna do it. sorry for the unsolicited advice..
to answer your question: I think it feels great and relaxing.