Now, this one is a hard one.
Some people say a little jealousy is fine, others say jealousy in general is unhealthy. The ones who say that are the ones that hate that their gf/bf are on them for talking to friends of the opposite sex. As in your opposite.
Jealousy, in my opinion, is ok if there’s a little. My girl gets jealous, I know it’s because she cares about/likes/loves me, but if she goes bat shit crazy cause she hears me on the phone say I love you too, to my mother, she’s gotta go. Ain’t nobody got time for that. Don’t be the overly attached girlfriend/boyfriend.
Now this also goes hand in hand with trust. If you do not trust your partner, than your jealousy will be super high, and that’ll just make it worse.