You need to think if you are happy to pay her £X to do those jobs, or if you want to pay her £X for a set amount of time. There are quite often threads onhere where people feel they are being 'short changed' by their cleaner leaving early. there are pros and cons (and she may have her own thoughts or preference) but some people get quite upset by it.
Generally, it will take a lot longer the first time and about 3 or 4 weeks to get up to speed. So that makes a difference.
You need to think about things like holidays (your and hers) or sickness. Generally cleaners are self employed, so if they don't work, they don't get paid. Some people feel if they are coming every week then there is more of an employer relationship to it.
You need to know if she brings her own stuff, or if you are providing it, and, if you provide it, is she happy with what you have or does she want particular cloths or mops or sprays or whatever.
If you are particular about the way things are done, then you need to be clear about that. After reading MN for many years, it AMAZES me what some people consider 'normal' my standards are a LOT lower than a lot of MNers
Other things I've read on hear that never occurred to me is thinking about insurance if you have valuable antique or arty, breakable objects around.
How you pay ? I leave cash out for my cleaner but some people object to that apparently. Obviously how much she charges.
Probably a good idea to agree to have a chat in a month or so to see if you are doing anything / not doing something that makes her job more difficult, and equally to ask her if she can do something a bit differently / more carefully / more thoroughly. Just keep open the communication really.