It won't even come to that, since your friend will probably be denied entry to Spain on 13 May (as it will be clear that she won't be departing the Shengen zone before 15 May).
So she does need to obtain a new visa.
Welcome to FT !!!
I assume that by saying a European visa you mean a Schengen zone visa (which does not cover all of Europe).
unless you have proof that you are leaving the next day, I don't think they will allow her in. In fact, the airlines check that during check-in and will not let her board. My mother's visa was one day short of the departure date and she had to change the return flight, costing her $200.
As far as moving from Spain to France, there is no border check but you may be stopped at anytime.
I would definitely get a new visa.