You'll definitely want to shop around, test ride and see what feels best for you. I'm also height challenged, as is my sister. Started out on a Felt ZW100, and my sis still has her Felt ZW95. We both liked the geometry for our body type (short waisted).

Depending on the type of ride you want, take a look at a Cannondale Synapse Alloy with 105 or CAAD10 Womens 5. Current price might stretch the budget, but you might be able to get a deal by finding a 2011 model. Carbon would be ideal, but you'll need to really hunt around to find one at your budget, and likely would need to find a good used deal.