Hi Pink,
a similar situation occured with my parents a few months ago.
My mum's name on her passport is 'Bridget', but she always uses the spelling 'Brighid'. So when she booked tickets to London with AerLingus, they were under the name of 'Brighid'.
So I rang AerLingus, and was speaking to a very helpful girl who told me that the rule is that if the name on the tickets differs from the name on the passport by 3 letters or less, then for european flights it is fine. (For USA flights there are more stringent rules).
So my mum flew with no problems.
I'd suggest you ring Aer Lingus again, and request to speak to a manager, who should be able to advise you of this rule.