The only problem with an electric guitar is it can be very expensive, even initially.
You not only have to consider the guitar, but also the amplifier it requires to be plugged into.
If you buy a cheap guitar, this can be very off-putting, because it may actually be set-up wrong, or just made with cheap components. and could be hard to play, and sound awful.
So, you need to do a bit of research by either finding a friendly music shop, and quizzing the staff (and if it is any good they will be more than willing to advise you, even as a complete "newbie"), or just by reading some of the reviews in the various Guitar Magazines that are available everywhere. They always feature an equipment review, and usually a beginners guide.
Some of the big names in Guitars (i.e Fender, Gibson) have associated companies that particularly make budget versions of their guitars, and they are usually made in places like Mexico, Japan, and even India. Quality varies, but it is a good starting place.
In general, the mainstream quality Guitars are usually American companies (Fender, Gibson, Rickenbacker, Gretsch) but you will pay many hundreds of pounds for these items. Of the non-american companies (and this is my own personal opinion only) Yamaha is probably the best quality for a budget outlay.
So, I feel you will probably have to pay up to £200 for a half decent guitar, plus another £100 for a small (good quality) practice amp. If, in the future, she does want to play in a band, the practice amp will have to be upgraded to something more suited to small gigs.
However, like any musical instrument, it is how the player feels about the instrument, so don't necessarily go for the latest "trendy" guitar if she feels more comfortable playing a less well known model. All shops will let you try the instruments, and I suggest you go several times until you find the one that she feels comfortable with. Take your time, a good shop will not rush you, and don't be put off by being a beginner. Ask any questions and don't get rushed into buying anything you're not comfortable with.
Sadly, I have recently had to sell 2 of my guitars (I'm skint), and I had owned them since the mid seventies, so do be warned that it can get a bit addictive once you get started.