Hi Jane. I live near Ipswich, about 40 miles from RAF Lakenheath. The base is, to me, a little bit of the US embedded in the Suffolk countryside.
Outside the RAF gates, Suffolk is a sleepy county. Lots of fields, agriculture, nice country pubs with open fires and beer (not lager, but our own 'bitter'!).
One problem new arrivals seem to have is with our roads. Of course, we drive on the 'correct' side of the road, whereas most others drive on the 'wrong' side.

With rural roads, there are rarely markings to guide you onto the correct side, so accidents happen. People also look the wrong way when crossing the roads, and are surprised by vehicles (especially in London where it's quite mad - traffic wise).
So basically, just remind her to look both ways, and be careful driving until they are used to it.
London is easily accessible from Lakenheath by train or road. Train is better. London gets totally mad near to Christmas though.
Hopefully, she'll love it here. Let me know if you need any more info.