You are going to need a guitar, amp guitar cord, strap, spare strings, picks, and if she doesn't have them already, and electronic tuner and an electronic metronome or drum machine. At an absolute minumum, a "gig bag" case, altho a hard case is a better option. Usually a stand, as well,
Don't buy used unless you know what you are doing, or have someone with you that does - the neck is the heart of the guitar, and it and the bridge have to be capable of adjusting out to playability,- or you just pissed your money away.
There are starter sets that have a small amp, a (usually) servicable guitar of Chinese or Indoneasian manufacture, frequently with a real guitar manufacturer's name on it, (think "captive knock-off" - the amp is one as well....), gig bag, strings, cheap strap, a few picks, and sometimes a tuner - usually, these are around $250 - $300. If you go this route, please buy from an actual music store, verses Hastings or a big box store - as having someone to check it out and adjust if necessary is a really, really good thing. Wood takes time to get stable and know it isn;t part of a tree anymore, and bouncing halfway around the world in a shipping container can promote warping and shifting - no biggee IF it can be adjusted out and IF someone knows how to do it.
Often you can find a used starter set , or you can get better quality buying individual used pieces. Avoid pawn shops like the plauge.
Any more
PM me & I'll give you a number to call me & we'll talk....