How much an Ukrianian need to have at the frontier

Hello.
I am french. I invite my Ukrainian friend and her two daughters to come in Italy for our holidays for 11 days.
I paid the hotels and apartment for the journey. She has her plane tickets for go and return flight.
How much she should have in cash at the frontier?
We are a bit lost with the prices.
I will pay all in Italy for them.
Thank you for the advice.
Sincerely yours.
Didier Fortin.