How about this: God is the source of all love, and so can be jealous - which means that He is due all love in return. He is love’s Creator and Owner. We, being the mere object and recipient of love, have a duty to return it to its source. We are not to be jealous, since we have no claim to love other than to have received it for the purpose of returning it. For man to be jealous in love is to attempt to usurp God’s role as Creator, Source and Owner of all love.
A crude analogy: God is a generator of electricity, and we are His light bulbs. He sends His electricity to us, expecting that we will radiate that electricity back to Him on the form of light. We have no right to be jealous of the electricity, since we did not create it, but only received it. He, on the other hand, has every right to expect that what He sends us freely will be radiated back to Him.