Topraise How much money are we talking about?
The mediator will go through the motions and then suggest that you split the difference, so you get half, the client gets half.
Then you can accept that and if the client also accepts, you get half.
If neither party accepts the suggestion, only arbitration can help.
she was happy with it and her response was great but to my surprise after some minutes she messaged me with unnecessary expenses
Sounds like the client was not the actual client but someone who farmed out work they were hired to do and the actual client was not happy.
What do you mean by "she messaged me with unnecessary expenses"?