This is a bad and misleading translation. I've reported it but I wanted to write it here for any confused learners.
We don't generally use "how" to ask about a description of someone. For that, we use "What ... like?" German uses "wie" for this.
Asking "how" when talking about a person will be assumed to be asking about a person's state of health or how their life is. In German, the most common way to do this is "Wie geht es", followed by the dative case.
Wie ist deine neue Freundin? = What is your new girlfriend like?
How is your new girlfriend? = Wie geht's deiner neuen Freundin?
No. It refers to some characteristic of the object (in this case the girlfriend). A possible answer would for example be "She is nice", "She is beautiful". For asking about the state of health only "Wie geht es deiner neuen Freundin" is accurate.
PS "wie ist du" is wrong, it would be "wie bist du" instead (although I can't think of any situation in which you would use that...)
Yes, but in the other direction, i.e. when you get the German Wie ist deine neue Freundin?, presumably only one translation (What is your new girlfriend like?) makes sense and should be accepted, and not the other (How is your new girlfriend?).
Is that how it already is currently? I can only speak to the first translation, which I put in, and which was indeed accepted.