My 20year old daughters resting heart rate is about 100, had a hoter monitor on 24hrs dr said ok. she has crohn's disease. what could be causing this?

There are many: causes of an increased heart rate. Did the holter show appropriate diurnal variation? With Crohn's this could represent mild dehydration or a systemic inflammatory response. Address your concerns with your health care provider since he/she has all the information. If you aren't satisfied with the answers, see a different health care provider or obtain a video consult.