Hello,
I was admitted to GW (my #1 school) with a $15,000 presidential scholarship. As much as this helps, it will not be enough to help me pay for tuition. Does anyone know how willing GW would be to match this scholarship with the amount I got from another college of a similar ranking? Any advice on how to ask them to match? Thanks in advance.
A lot of people typically appeal their FA award by sending a letter along with copies of other financial awards from other schools, to try and convince them to make their award more competitive. While there are no guarantees, it’s definitely an option and a lot of people do it. It will obviously work better if you’re a competitive, regular decision applicant who could contribute a lot to GW, being that the FA office will want to offer more money to you if you’re really intent on enrolling.
I agree with @karaakirsten in that your best bet would be to show GW your other offers. A well-written letter couldn’t hurt, either 
Thanks for your help! Would you suggest speaking to the financial aid office in person or writing a letter?
If you have the option of showing-up in person you can definitely try that, but I wouldn’t stop by without an appointment. I don’t know how busy the folks in the office are, but at admissions time I assume they’re busy. Try calling first to explain your case and ask if it’s possible to meet with someone in person. It’s possible that they’ll hear your case over the phone instead.