Out of touch with rates now so not even sure what basic single persons code is, sorry, but the general rule is stick 5 on the end of the code and it tells you what they are entitled to earn tax free each year.
So a code of 795 would allow her nearly £8K a year tax free!
She really needs to hassle the IR to get her code changed - you must pay her under the code they have issued until they tell you otherwise unfortunately.
Right, just checked. Standard 'normal' code is 486 so that allows approx £4860 per annum.
She has roughly £760 free pay left so would assume code should be in the region of 76 but don't quote me on that. There might be other variables that have to be taken in to account that only the IR can decide.