Hi Matty,
I'm sure your wife won't be qualify for ILR because she's been only here for 3 1/2 years with Working permit.
After marriage I think the next step for your wife is to apply a spouse visa and she can still work with any employer with this visa.
When near completing her 24 months stay/living together in UK she will be then qualify to ILR.
I'm not sure about your plan to her daughter.... It's not really a good idea to apply her as a visitor visa then switch to permanent stay...I'm sure this will give you a lots of hassle when you do this.
Why not apply her as dependant instead of visitor?
