as there is an 11 t cog on the Cassette, I'd lose the 53t chainring,
46:11 is going to be plenty high ,
particularly after getting used to spinning in those classes .

yea 175 is too long a crankarm , unless she is long legged and say 5'8" or so.
contrary to spinning.. where a shorter arm on the crank is better ..

what is on the Gym machines she is used to?