I'd be flattered more than anything. It says to me she liked your DD's name but didn't want to *exactly* copy it so she changed it slightly to avoid this. The kids aren't likely to notice even if they do see each other a fair bit. Or if they do, will likely just think it's funny not be upset about it.

In my family we have cousins named David Jonathon and Jonathan David. Neither of them are particularly worried about it.