I think yes

彼女 does also mean girlfriend, so, yes. Usually, names are used instead of 彼/彼女.

Exactly what I put when I first met this.

Yep. www

It's not the end of the world, duolingo is really just to break the ice for more formal study like textbooks... yay

The difficulty in Japanese is that many words have multiple meanings and many kanji have multiple readings... There's a lot of context clues involved in figuring out meanings.

Agreed. I would actually be interested in paying for Duolingo if they provided proper educational notes on new word as they were introduced, and how they should be used. Just having that dumb owl pop in every so often to tell me I'm learning a lot is nothing. I don't feel like I'm really learning anything here, just memorising things.

Words can mean different things based on context. The popup shows all meanings including ones which are invalid in the current sentence. The popups are just hints. There's a good comment higher up which explains why this can't be read as girlfriend here.

Yes'mstve

y'all've

彼女(かのじょ) is “she” (when it’s not “girlfriend”). “who is this/that woman” should be この/あの女の人は誰ですか if I’m not mistaken.

Are you talking about the ょ in かのじょ? It basically means that this Kana should not be read with its full pronunciation (in this case “yo”) but combines with the letter before or after (in this case before) to a single syllable. By far the most common uses of such small Kana are these two:

1. A small kana from the y- series (やよゆ) following a regular-size Kana whose pronunciation ends in -i. This means the -i is deleted and the two combine to a single syllable. So for example みょ is pronounced “myo” (contrast this with full-size みよ “miyo”). This is also the way to write syllables with initial sh- or j- and a vowel other than i: しゃ sha, じょ jo etc.
2. A small っ simply means that the following consonant is doubled. So where かた is be read “kata”, かった is “katta”.

(I used Hiragana for the examples but obviously the exact same rules hold for Katakana.)

“Is that your girlfriend” is a yes-no question, not a “who” question ;) As far as I can see, かのじょはだれですか could mean “who is [your] girlfriend” (with the “your” just being implied) given the right context, but I may be wrong there (maybe a native speaker could weigh in?).

“Is that your girlfriend” should be something like そのひとは[あなたの]かのじょですか？

It's supposed to, but it doesn't work very well for Japanese.

“This girl” would be この女の子 though, wouldn’t it?

I’m not completely sure what you mean. かのじょ is the base form of the word and that doesn’t ever change either. The じょ part is a single unit which can’t be split up (it’s also just a single kanji 女 in kanji spelling). かのじ would just be “kanoji”, not “kanojo” (note how it’s a small ょ, which means it modifies the pronunciation of the preceding じ).

No. “her” is the object form of the pronoun, and we need the subject form here. After all, the answer would be: “She is…”, not “Her is…”

No, it’s not. First, the word order with the question word in its “original” position rather than at the front is unnatural under normal circumstances (it’s possible, but restricted to contexts where the speaker is extremely astonished by something and wants the other person to repeat that part of the sentence).

But even disregarding that, “whom” is the old object form of “who” (e.g.: Whom did you see? To whom did you write? But not: *Whom saw you? *Whom wrote to you?). However “to be” doesn’t have an object, but rather what grammarians call a predicative (basically a sentence constituent which is part of the predicate (verb) but denotes a quality of the subject or object). In a lot of languages, including, predicatives have to agree in case with the thing that they refer to (i.e. in our case the subject). Therefore, the thing after “to be” should always take the subject form rather than the object form. This is the reason why grammar Nazis will insist that “it is me” is incorrect and the correct form is “it is I”.

Now of course language is constantly evolving and “it’s me” is indeed the preferred form for pretty much everybody (besides grammar Nazis) these days. However during the same time, the object form “whom” has also fallen largely out of use. It seems that for most speakers today, “whom” has almost the same status as “thou” now: A marker of old-fashioned (or even archaic) style. But like with “thou” and the associated verb endings, people also increasingly misuse it because they don’t actually use it in their normal speech. In any case, I have never seen “whom” used with “to be” in earnest. To me it sounds like the kind of cringy pseudo-archaic stuff you might hear in a bad role-playing game: “Oh king, thou cometh from far away. Whom was it that hast brought thee hence?” (Almost every second word of which probably causes whatever is left of Shakespeare to roll over in his grave).

Actually, technically aye (despite the complaint below about it being the accusative form). However, it is most assuredly archaic even amongst the small group of speakers who still use that register.

Go somewhere else you pretentious bragger