Please help explain why.
My daughter just turned 21. Her Boyfriend of one month (who is her first boyfriend) gave her a charm necklace as a birthday gift. We took him with us to dinner. When we asked what time he needed to be home he replied 9 or 9:30. We took him home late (around 10). Upon returning home, my daughter posted a picture of herself wearing the necklace on Facebook. A few minutes later, his mother posted a picture of herself with a similar necklace that he gave her the same day. We are confused as to why he would do something like that. Is it reasonable for my daughter to be upset by her boyfriend giving his mother a gift on her birthday?