Cliche phrase, but you should never deposit all your hope of ever being happy into another person. I say that with experience. Of course, it's easier said than done. First step, stop monitoring whatever they do, it will only bring you pain even if it's a silly situation that you don't even know the full context.
If you go down this rabbit hole, you will start comparing every single aspect of your relationship to the one she has with this dude. It's not because she added another person and was joking around with them that she doesn't care about you.
Do you love this person romantically? Does she know?
But you're not in the wrong, no, jealousy is completely normal when a person means that much to us, even when it seems a bit dumb. I've been through that and it still hurts me. Sending virtual hugs