It is pretty but very overused and a bit boring, in my opinion. I don't think of it as being dated. I know three - one is four months old, one is aged about four, the other is nearly 30 (she was known as
Jessie until her teens, she now goes by
Jess). I also knew an old lady called
Jessie (not short for anything).
I hear of a lot of young girls being called
Jessica, not surprising seeing as it has been in the top 10 in England for the past ten years.
I think will remain fashionable for a while. It has a classic feel to it.
I like the nickname
Jess or
Jessie. I've never heard of
Jessa but I think it works on it's own.
Jessie has historically been used on it's own, with no connection to
Jessica, but I'm not sure about it personally. It sounds a bit babyish.
I love the name
Jessamine! I'd use
Jess as a nickname.