As a rule, if you have more than 3 people who need their hair and makeup done on your wedding day, hire two separate people. If you have a Hair Stylist and Makeup Artist in one you risk running late on your big day.
I am often asked if I do hair as well as makeup and the short answer is "no".
I have not been trained as a stylist - I can barely do my own hair! When I became a Makeup Artist, I had the option of going to school for styling but I decided I just wanted to focus on different aspects of makeup artistry instead of becoming a jack of all trades.
I have found that people that do both usually excel in one over the other. In my television experience, I have had to do "light" hair styling (curling, a blow out, etc...) but I have never claimed to be an experience or skilled hair stylist.
Makeup and Hair in one is hard to come by. Attention brides, if you are the only one who is getting styled on your wedding day, it's probably best for you to find one person who does both - it's the more affordable option.