Shady or no?

A girl my husband works with - not closely with but in the same building - added him to Facebook. She does have a boyfriend and is 22 but she looks very much younger. He had mentioned her name before saying that it was so and so’s sister in law and she was really quiet.

A day after he accepted her friend request, she started messaging him random things like weather articles. Completely out of the blue. I was like what in the? Like I wouldn’t expect anyone to send me things if we hadn’t previously discussed or expressed interest or worry right? A couple other people he works with are also friends on My Facebook and he’s said nothing about it. When I said I was going to request her as a friend he went off and told me to not start trouble excuse me how is that trouble?? I told him that just makes it seem shady as hell getting all defensive over me just saying I thought about it!