If she can cover 14 eggs that would be fine, but unless she's a big girl, or fluffy, I'd be surprised if she can consistently keep that many under her and warm. My girls can usually handle around 10 before I start finding eggs sitting next to, but not under, the hen. I have a variety of breeds, but Wyandotte, Welsummer, Rock, etc so average sized large fowl.
If your rooster was fertile, the girls can store the semen for around 2 weeks and use it to fertilize eggs. One reason if you want to be sure of a specific breeding, you need to give the hen at least 2 weeks with the chosen rooster(s) before you start collecting eggs.