I wouldn't risk leaving it until she checks, it could result in an unpleasant and non-productive confrontation at the airport. I would go the airport before she travels, with the printout, and speak to a duty manager or someone senior, and get them to agree in writing or in the presence of a witness that the needles will be accepted.
I travelled with a friend who is diabetic and had her injection stuff with her (it may not have been needles, sometimes they have a little device which is not actually a needle and syringe), on easyJet from Geneva to Barcelona, and we had no problem. I don't see why the regulations would vary from country to country within Europe.