I can sign using BSL and I am aware that there are some serious differences in some of the signs in BSL and ASL. That said, as I understand it, there is still a great commonality between the two systems. (I think that with finger-spelling, "Z"
is totally different!)

BSL is increasingly being taught in Scottish schools to hearing-children, so the number of BSL users is on the increase. Probably the most useful signs would be the same as in any foreign land, such as
"I am an American"
"Can you help me please"
"Thank you"
"Please"

But since your friend is coming to work with the deaf community, her best bet would be to make early contact with a signing-adult or interpreter to discuss the language differences. We do have an excellent Deaf School (Donaldson's), who have just moved from their old castle-like edifice to a purpose-built building. BSL is also taught to children with learning difficulties as a means of improving their communication skills.

I do hope your friend enjoys her stay with us