jealousy is a part of human nature just like anger, but it should not be taken to the extreme. I see extreme jealousy as being selfish and ungrateful as times- so yes, a lack of love for this world or unappreciation for what Allah (SWT) has provided. I don’t know if you can label that as lack of understanding deen or imaan.
I don’t know. I’m honestly not much of a jealous person and it annoys me when I come across other women who are jealous of others. The ones that are like that are usually jealous of wealth, those who marry rich, have the big house, nice cars, loving husband, etc. I don’t understand why people can’t just say MashAllah and move on. The other form of jealousy I might see is in academics; maybe parents are responsible for that.