Jul 10, 2017 - 05:06 AM
To say "She's fine", native speakers will always use "va": Elle va bien. In the context of asking how someone is feeling and for greetings, it would sound very strange to use "être", so my recommandation would be to stick to "aller" before "bien". "Elle est bien" would only be used in very specific contexts, like Fabrice said, to mean someone is comfortable, or to describe someone as great in what he/she does, as in "How is your new teacher? She's fine" -meaning she's a good teacher: Comment est ta nouvelle enseignante? Elle est bien.
Apart from those contexts you'll hardly ever hear or see "être" before "bien". Hope this helps!