I believe the following is true for both UK CAA and FAA licenses.
You can have lessons at any age.
Only lessons received after the 14th birthday can be counted towards a license/rating.
You can go solo at 16. At this point you are flying on the instructor's insurance, cannot carry passengers (except an instructor) but otherwise you can go where you like, within the UK.
You can pass the skills test (the checkride) at 17.
Education (or lack of) is irrelevant. For the European PPL she will have to pass around half a dozen exams which is hard if somebody is completely thick
but if she can read and write and has a shred of common sense she will be just fine.
You mention a CPL and a PPL. I take it you mean a PPL. It does indeed take a year on average to finish a PPL in UK's weather (lots of cancelled lessons) but with luck it can be a lot quicker - especially if the student has been doing "informal flying" beforehand and knows the ropes.