Since college is technically temporary, students are usually considered to be permanent residents of the state they came from. The concept is called "domicile" and a taxpayer can have many residences but only one domicile at a time. Your domicile is where you have your most substantial connection.
What makes you a resident? Generally, you're a resident of a state if you intend to either stay there permanently, or return there after a temporary absence. It's where home is – where you come back to after being away on vacation, business trip, overseas employment, or school. Many other factors are considered, not the least of which are where you are registered to vote, own homestead property, your children attend school, and are licensed to drive, (
If you have permanently left your parents' home and have moved in with your fiancee, and visit your fiancee on breaks, you may be domiciled in Dover. If you still commute between your parents, your school, and your fiancee, and still have your bank accounts and voter registration at your parents' house, then you are probably domiciled there.
The least likely answer is that you are domiciled where you go to college, for the reasons I mentioned above. (Unless you plan to be a permanent resident of GP and your fiancee plans to move to VA to be with you.)
You can't really pick and choose based on who has lower taxes, it's based on the facts and circumstances of your life.
If you are a resident or domiciled in state A and go to school and have a job in state B, you will owe income tax and a non-resident return to state B and a resident return to state A. But state A will give you credit for taxes paid to state B, so your overall tax should not be higher than the higher state alone.
Also be aware that every state wants their fair share (or more) so you should really look at the rules for establishing taxpayer residency for the 3 locations involved. The last thing you want is to be in a tug of war between two states that both insist you are a resident. Check on the state tax web sites for the rules to be considered a resident of each state.
