mediation .......Financial

I need some help so I can make the a decision on what my next move is.
I will be attending mediation for children arrangements, however my STBX has indicated at our mediation initial hearing that she would like the finances to be discussed at mediation, but I''ve not agreed.

My thinking is that she may not want go to court as she has herself and persuaded me to hand over out large sums of money out of our savings to pay her back her mother who at that time gave it to us.(no formal agreement)My STBX is obviously saying now it was money borrowed that has been paid back. (we''re not talking small amounts)

Firstly, Am I correct in thinking that if I want to apply for a financial order, I would have to attend a mediation assessment and have a FM1 form completed by mediation before I consider making a application for financial order to court?

Secondly, has anybody had similar experience of their STBX financial bad behaviour. (I''ve also learnt that my STBX was making high cash withdrawals on a regular basis in the last year or so) - still waiting for her explanation on this from the form E disclosure....

All I want is a fair trial as I will have nothing left........