Any of these can work. You can short cycle her with a shot of prostaglandin (Lutalyse or Estrumate), but that only works if she's between like Day 6 and Day 16 or so of her cycle. MGA is a feed additive used in feedlots to keep heifers from cycling, and I think I've read about it for synchronizing heifers, but I'm not sure about that. I'm not aware of any negative side affects, but I've never used it. A CIDR would also work...basically anything you might use to synchronize a group of cattle could be used to manipulate one's cycle.