Sorry, this is extremely convoluted. Also, NC as it's a bit identifying.
I've just realised my DD has the same first and middle name as my aunt. My aunt doesn't know this and I haven't told her, because DD is not named after her. She only knows my baby is named after her mother (my grandmother.) I don't know whether to tell my aunt as I don't know whether she would think it was a nice thing or slightly offensive.
Let's pretend my DDs name is Maria Georgina. Maria is after my grandmother (auntie's mum). Aunt is called Georgina, which also happens to be the feminine version of my DHs father's name, George. (In his culture, people name their children after their parents.) Aunt lives in another country and has never met DD. However, we keep in contact over email and meet up maybe every five years or so. Nobody in my family has a particularly good relationship with my aunt and her behaviour can be difficult sometimes, but I like being in touch with her as I don't have many relatives.
Aunt has just told me in her last email that her full name is actually Maria Georgina, i.e. that she shares a first name with her mother. (It's normal for people from my country to be called by their middle name instead of their first.) Aunty told me this because she knows my baby is called Maria and I guess she's happy that they share this in common. She doesn't know they share the exact same two names.
Aunt has no children or close family and I think our relationship (scant though it is) means a lot to her. I don't know if I should tell her "oh, incidentally, DD is called the same thing as you because of DH's dad". Or is it slightly offensive to have called her this even though this is my aunt's name and she isn't named after her? (I didn't really want to do this, for this reason, but it was important to DH to honour his dad.)