My eldest didn't tolerate cows milk at 13mo so I didn't offer again until 18mo, by then he did ok, to this day he still doesn't drink much of it (unlike his brother who didn't have any dairy until 10mo & no milk until 17mo & loves it) I'm pretty sure that is because, like me, he has a low tolerance for it (I was taken off it for 3 years as a child) & can really only cope with the small amount I have in a coffee unless (like Deb says) it is cultured.
If it bothers you I'd stop & see if her gastric system matures in a few months take it month by month.