Have you thought about a spring powered rifle perhaps? No need to bother with all the air tanks, refills and hoses then. Something like a Weirhrauch HW95 is a light and compact, good quality rifle. To be more precise regarding advice it would help to know what disciplines she fancies getting into. If it's 10M target then there would be better alternatives. But for FT and HFT style shooting it would be a good choice.