To not change my newborn DDs name

[Skeetle]

My DD was born last week and we've called her Jennifer. We spent a long time choosing names which was difficult as we wanted a recognisable, classic but not very common name and DP and I have very different taste We're very happy with the choice and we've told family and friends.

My partner has a son from his previous relationship and his ex has a 2 year old DD with her new partner. Her DD is called Guinevere, though most often known as Evie.

My partner has just had an email from the ex saying that she's not too happy with our choice of name. Were we aware that Jennifer is the Cornish derivative of Guinevere, she doesn't think its fair on DSS to have 2 sisters with 'effectively the same name' and she thinks we should change it to something else.

We did find out there was a connection between the names when we were looking up Jennifer after deciding we liked it. However we felt they sounded so different and that not many people would be aware connection that we discounted it as a problem very early in the process.

I don't want to change her name. AIBU?

She's completely mad.

Actually if you say both names out loud they don't sound similar at all. The only to link them is that are three syllabe names.
Lots of names have derivatives. What are you going to do?

Thanks for all your replies. :)

Well, we've decided to do what we usually do with her rantings emails. He's answered any of the points that are worth answering or need an answer in her email and we've completely ignored the paragraph on the names.

It was very tempting to have tried some of the suggested responses (or my friend's who says we should tell her we only chose Jennifer in preference to Guinevere as Guinevere was just slightly too pretentious for our taste).

However, its more important to try to keep the peace.