Jealousy is simply a showing of a lack of trust. The amount of trust being inverse to the amount of jealousy. If one trusted another 100% it would be impossible to be jealous of them.
To not be jealous of another is a compliment to them. However, if the other person is insecure they are apt to feel a lack of jealousies as proof of a lack of love. This can lead to a dammed if you do and dammed if you don't situation.
Love and jealousy have nothing in common. It is perfectly possible to be jealous of someone without being, even remotely, in love with them.
Jealously, unaffiliated with love, is a combination of lack of trust and ego threat.