This comes up from time to time on the forums.
From what I remember, there's nothing that explicitly says a Ring / Circle spell has to be spherical. However, there are various "Ward Against the Faeries of the X" spells that say things like "Seen from certain angles at night, the ring appears as a [colour] dome" (for example, the ReAq one is light blue) which suggest they are at least some of the time. It's therefore a house rule as to whether Ring / Circle spells are always spherical or not (and if you rule that they don't have to be, you also need to decide what happens when someone turns one through 90 degrees and scrawls it on the wall).
Yes, but tracing the ring is rather trickier if it's 4-5 feet above her head. Not undoable, but trickier.