You need to ask for a full refund not partial, as she is in breach of contract by not completing the service as agreed.
Assuming you engage another MUA, you will need to pay for another trial as well as make-up on the day.
Do you have any written agreement? Complete a small claims form, copy it and send it to her giving her 7 days to refund you otherwise you will take her to court for breach of contract.
A trial is useful for both the Bride and the service provider to make sure they are a good fit. So, it's not uncommon for Hairdressers, MUA's, Nail Techs etc. to decide they don't want to offer the wedding service if they feel that they are dealing with a tricky Bridezilla type family, for instance.
I'm not suggesting for one minute that the OP or her daughter are overly demanding but I am pointing out that very occasionally, you just feel it's not worth your time and will be far too stressful to get involved. Equally, other factors might crop up making it difficult to provide the service on the day.
Either way, if the service provider pulls out, they should immediately offer a full refund.