Whilst everything is rosy now, if (god forbid) you separate, she may try and claim. My suggestion would be to have a document drawn up stating that the property is yours and yours alone and any contributions she makes to the joint finances will not give her a beneficial interest in the property.
Ordinarily, contributions to daily living expenses will not result in a beneficial interest. Unfortunately, I have seen cases exactly like this where the ex has claimed that promises were made and she relied on her detriment to those promises. Whilst ultimately she may be unsuccessful, it will cost you in the long run in having to fight it.
Me and the FH have a very simple agreement - his house is his and my house is mine. Any contributions I make (I am the only earner) do not entitle me to an interest in his property. Any money I spend on fixtures or permanent improvements stands as a debt in the case we split up, but I will seek no interest in his property.