This may turn into one of those "learning experiences" that you will not want to repeat.
I also totally agree with the other comments that price should have been discussed before proceeding.
This also sounds like something you have not done before, so how would you know how much to charge?
Is this person a friend of yours? relative? any idea of her financial situation?
Anyway - you are where you are now -
In my limited experience, people that do not sew think you can charge less than Walmart for anything sewn -
And when I have agreed to a project, most times it has taken way longer and been more complicated than I anticipated.
Good luck.