Higher education dilemma - in UK or USA?

Hello all,
We're an American family currently living in the UK (Colchester, Essex). My husband has dual citizenship (American and Irish). We've been here for about 4 months. Our youngest daughter is attending a local sixth form college and is in the first year of the IB diploma programme. I've copied and pasted my query from another forum, in the hopes of getting some more feedback. She is in a quandary as to whether she should stay for next year or return to Oregon (for educational and/or financial aid reasons).

I have several questions, but will begin with just two. The first one has to do with the availability of financial aid and scholarships for US high school students studying abroad (for high school). My daughter, currently the equivalent of an 11th grade high school student, is studying at a sixth form college in the UK and is the first year of the IB diploma program. If she stays on a second year, she will receive an IB diploma, but as she wouldn't be in the USA, would not receive a US high school diploma. In this scenario, what I need to know is whether she still be able to apply for financial aid and scholarships? So many scholarships want to see a GPA and a high school diploma or equivalent. Here's the thing -- she can return to her US high school in Oregon to complete her final year, whereby she would get her US high school diploma and she would also complete the AP Capstone diploma program. As a Sophmore, she was enrolled in the AP Capstone diploma course. She took three AP courses and four AP exams. She also took SATs and ACTs (and is going to retake the SATs this May).

We/she is trying to figure out, from an educational perspective and a financial aid/scholarship perspective, what she should do -- stay in the UK and complete the IB diploma or return to Oregon and get the high school diploma and the AP Capstone Diploma. She will need as much financial assistance as possible; therefore this is a top priority for her/us.

Next, she is interested in applying to both US colleges and UK universities. My second question has two parts: is there an advantage to applying as a current UK student to either US colleges or UK universities (she will NOT be considered a home student for UK universities as she would only have resided in the UK for two years (but she will have a residency card) As well, does anyone know about both FAFSA and other financial aid if she applies to UK universities? If so, are there specific UK universities?

Thanks!