What would Emily Post say?

My mother received a baby shower invitation in the mail this week addressed to her, my sister and me. This has happened approximately 50 times in the past ten years and each time I shake my head and roll my eyes. Just a couple months ago, my mom got one invitation that said, "Linda and girls." I understand and agree with the one-invitation addressed to mother and daughters when you are in high school (or younger). Or college. Or maybe, just maybe, if you're still living at home with your parents. But none of those things hold true for me. I am 32 years old. My sister will be 35 next month. When I am 50 will my mother still be getting mail addressed to "Linda and girls?"