Lactose Intolerance Support Group
Lactose intolerance is the condition in which lactase, an enzyme needed for proper metabolization of lactose (a constituent of milk and other dairy products), is not produced in adulthood. A hydrogen breath test is required for a clinical diagnosis. With lactose intolerance, the result of consuming lactose or a lactose-containing food is excess gas production and often...

It's not an easy thing to diagnose by doctors. Best thing to do is to not eat any dairy at all and see if she feels better. Sort of eliminating the dairy for a week or so, and see if she is doing better. No non-dairy ice cream, no Lactaid tablets.
Try that for 1-2 weeks and see if she feels better. Lactose intolerance is kind of a trial and error thing. I can eat yogurt now, but it took awhile to build up to that.
There are also books you can read that say what foods are okay for her to eat, because she needs to have calcium in her diet.
I have managed to avoid dairy and it's fine. You get used to living like that and I don't miss it.
She is 10. This past week she has been vomiting even from lactose-free ice cream, too, and her parents are puzzled! Also, even after taking the capsule. Thank you for your advice.
I don’t know what happened to change my dairy intake but I never did have anything like it as a young child and it is still really confusing to this day. I just deal with my stomach issues as they come up on what ever day it happens.