Why are women so materialistic and jealous over what other women have?

I see all these women with great lives that aren't happy. I see one with a great guy, great family, awesome job, and she's hot. Of course she's jealous of her friend who has really none of the other things but has the same car as her 2 years newer. Her jealousy shows and she talks about it all the time.

Why can't women be happy ever?