Soldato
When my mrs moved in some 10 years ago at first we had arrangement C and I was fine with that. Then when it was more serious and apparent that she wasn't going anywhere we moved to arrangement B. This worked fine for about 6 years then when I sold the flat about 3 years ago we bought a a place together and have arrangement A.
Sit down and work out what works for you both and it shouldn't be too much of a chore.
This is the right attitude.
She can help contribute a bit and then slowly ramp things up from there. No point moving her in, adding her to the mortgage and then deciding that you guys don't work together 3 months down the line.