Hi there I just want to reassure you regarding the Ielts testing and totally agree with my friend Terpe as in your wife has been here 3 years so there should not be a problem attaining the grades she needs.
My wife actually has just done Ielts testing and got an average of 6.5 across the board for her nursing career here in the UK but has to resit because she needs a 7 overall and she got these grades only been in UK for 7 months.
Your wife just requires Ielts level 4 in speaking and listening to pass this and these 2 elements are easier than reading and writing as my wife confirms to me ie: her results were speaking 7.5, listening 7 it was the latter 2 that let her down as now she resits.
I hope this can bring you hope that even though its stressing she should have no problems.
Wishing you all the best...
PS: She will take all 4 elements on Ielts even if she doesn't get level 4 in reading and writing as long as she gets that level in speaking and listening then thats fine UKBA will disregard the reading and writing part...