She's silly cause she's a young girl. The girl's feed off each other's sillyness, and Tayeon is a big part of it. She's one of the reasons the group is so fun to watch.
But she's always serious and seems to have a very level head when she has to.
Tiffany also says she scolds her all the time
And I remember Sooyoung mentioning Taeyeon scolding her about cleaning her room.
And I think I remember someone mentioning that she usually wakes up early and cooks breakfast or something? She's like a mother