I totally get this seems really trivial, but my Dsis gave me a Christmas card addressed to my first name and maiden surname.
I've been married over 15 years, so this feels a bit passive aggressive?
There is NO way she forgot my married name, as she's used it a lot, and the card was hand delivered.
I know she probably disagrees with me changing my surname, as I married relatively late, but didn't want any future children to have a different surname to me (DD1 was born the next year).
I know it seemed hypocritical to her, as it means DS had a different surname to me after I married (he was an adult).
DS had my maiden name as his dad refused to be put on his BC (not that it mattered as he wouldn't have had any parental responsibility even if he was put on it).
I know it's trivial, but Dsis has always been a bit weird about DH, even trying to stop me marrying him on our wedding morning, so the card addressed to my maiden name just feels a bit weird and shocked me a bit (she has addressed it properly in the past).