Does my neighbour's loft conversion change the terms of our lease/shared freehold?

[macca08]

I live on a ground floor of a victorian terraced house. Myself and the woman that lives in the flat above me brought the freehold together. She owns 2 floors. Currently, if any work gets done to the property I only have to pay one third (as I have 1 of the 3 floors). She has now told me that she would like to build a loft extension which means she will now own 3 floors to my one. Should this change the proportion of any future works I need to pay?

I think you still pay 1/3 to her 2/3 but you need to see a solicitor to check as also she may not be able todo this without your say so