My daughter was up literally all night vomiting, she is 9, what can i do to help her. someone suggested benadryl, (diphenhydramine) would that help?

No: Benadryl (diphenhydramine) is unlikely to help unless vomiting due to allergic food reaction, which would have resolved during the night. The key is to make sure she can rehydrate. Follow your instincts, but a trip to the pediatrician may be warranted (prescription for an antiemetic such as Zofran) and to make sure she is not dangerously dehydrated. Avoid motrin and other nsaids as well (irritates stomach)