J'ai envie d'elle.
The correct answer is: I want her. Is this sexual? Something I should not use to mean, she has a great life and I like her shoes?
I agree with 1km about this. I think it is possible that "j'ai envie d'elle" could have the meaning you asked about - that is you admire her, are mildly jealous. would quite like to have her lifestyle. It is unlikely, however.
In real life, I found that "fancy" and "have an urge" are workable equivalents.
Translations of these sorts of words and expressions are the most interesting. In real life you can't avoid context. In Duolingo you are totally sheltered from the context.
Added: Very comeplete dictionary entry here: http://www.cnrtl.fr/definition/envier
"J'ai envie de ..." means "I want ...", not "I envy ..." . And if the object of your desire is a person, it's lustful. You can use the verb "envier" instead: "J'envie sa vie et j'aime bien ses chaussures." Since "envier" hints at jealousy, "aimer bien" is a useful phrase to learn.