Bit of an essay below, but hope it helps.
If she hasn't come via a recommendation ask for references, and check them.
Write down a list of things you would like done and discuss it with her. Any cleaners we've had seemed to prefer when we talked through expectations ahead of time rather than just being left to 'clean'.
Set out what level of activity you're comfortable with - so, do you want them to change bed linen/take clothes out of the drier/iron?
Or just scrub the bathrooms & kitchen, and surface clean (so dust/vacuum) the rest of the house?
Would you want one additional room focused on each week?
Will you occasionally want items like the fridge/windows/oven cleaned and will there be an additional charge?
Are there any particular items you want done a certain way and is she comfortable with doing it? (Again could be ironing, or skirting board cleaning or moving items to clean under them type things)
What are the terms and conditions for holidays and cancellations?
Does she clean on her own, or will she have other people with her?
If you do decide to take her on, then check if you need to buy anything in terms of cleaning fluids/cloths etc., ahead of time.