I think the answer is yes a doe will breed more than one buck.

The doe will only stand for 1-2 days.......this would be the 1-2 days we see the buck and doe together but not chasing(often times in an isolated area as he has driven her away from other possible mates)

If during that 1-2 days they encounter a more dominant buck I'd say yes she will let him breed her after he chases her boyfriend off.

Just my opinion based on observation.