Well, I have seen women positively expressing their jealousy in subtle ways and winning psychic battles over other women who were a threat.
Many times, it is very subtle and can be as simple as letting another woman know you exist.
No need to be explosive
As I said, if used wisely, it is truly a weapon that can save a marriage or a relationship.
In my opinion, the fact that you bf talks with another girl is not yet a reason to give up on the relationship.
It would be a pity.
Here is an example:
Your bf chats with a girl at a party.
Many women might feel slightly threatened by that.
Rather than withdrawing and feeling miserable, you can walk to them, look at her straight in the eyes, smile and say: "Hi, I'm Jane, Paul's girlfriend..."
Often that's all you need to get your message through and it works!
Is this still an expression of jealousy?
It is definitely a battle strategy that shifts the power balance in that situation ;)