My DD also hated tummy time. She started crawling at 8 months. It seems she's been a bit slower than average (still perfectly normal) with gross motor development and a bit faster than average (still perfectly normal) with fine motor skills.
Also, crawling isn't a true milestone -- milestones need to be met, and they need to be met in order, or they can indicate a problem. Babies don't have to crawl, and crawling can happen "out of order" from the other gross motor skills.