Joint or Solo application?

We are in a little bit of a strange situation and i'm not sure if im doing this wrong..

Basically I work in Leeds, my GF works in Manchester and we live between the two paying for it in travel. She is now pregnant and we are planning to relocate to Leeds. We currently rent and will be FTBs.

My plan was to get a mortgage based on just my income and I have spoken with a broker and had an agreement in principle for the figure I was expecting. Funds for deposit etc are all in place so everything is good on that front too.

But I was reading about other people living at the property having to sign the mortgage agreement too ? The thing is she does have an income but we are not including this because we don't know how this is going to pan out.

She will be receiving maternity pay from her employer and there is also the chance she can transfer and get a new position at the end of the maternity period. As this depends on vacancies at the time, it is not guaranteed so I assumed it was best to just exclude her from the application process all together.

Am I doing this wrong? Should she be on the application with some sort of income? or on the application without?