My girlfriend is working in accounts payable for a small to medium sized retail business here in Virginia. She keeps a timecard and is paid hourly. Her office is telling her that by law they are required to deduct 30 minutes for lunch even if she works straight through.

Is there any law, Virginia or Federal, that requires a company to deduct time for lunch, even if one is not taken?

If the answer to the above question is no, is there any law that says they can not deduct the time if she does in fact work during that 30 minutes?

Along with the short answers, I am also looking to find source information to support one side or the other

The answer is no, there is no law in Virginia that requires the employer provide a meal period unless the employee is under age 16. However, if the time is worked, it must be paid. Period. If she is not, she can file a claim with the state Dept. of Labor for unpaid wages. See here:
http://www.dli.state.va.us/whatwedo/labor_law/claims_questions.html

Here is a discussion about meal periods and working during them:
http://a257.g.akamaitech.net/7/257/2422/12feb20041500/edocket.access.gpo.gov/cfr_2004/julqtr/29cfr785.19.htm

A point though: Law or not, the employer has the right to insist that an employee take a break. They cannot withhold pay if the employee works through that break, but they can discipline the employee in any other way they find appropriate up to AND INCLUDING termination if the employee fails to take a break when the employer wants them to.