What is the English word for "young woman"?

You need to realise that very rarely you can translate word by word. Regarding you’re alternatives: If you called my granddads “broad” she wouldn’t have an idea what you meant. My daughter on the other hand would slap you really hard. It’s not slang, it is a rather outdated but severe insult. “Young woman” is perfectly fine to describe a young woman.

If you can't use girl, you could try

lass n

1. a girl or young woman
   _{TFD Online}

This is probably borderline archaic or dialect-dependent, however, but other terms are that as well: maid, maiden, lassie, colleen, etc.

Your purpose is this:

the main motivation is to respectfully compliment a middle-aged woman by referring to her as young woman

The answer is that what you’re trying to do can’t be done without a non-negligible chance of offense to the woman.

You mean well by this, and there are some women who enjoy being labeled young (“miss”, “girl”, “lass”, etc.) but there are a significant number of women who don’t see this as being respectful, instead seeing it as being superficial, ageist, or infantilizing.

See also:

• Why We Need To Stop Referring To Women As ‘Girls’
• Why I hate being called Miss
• Don't Call Me 'Young Lady'

The OP is looking for an English term that satisfies the following conditions.

(1) Its literal meaning is young woman.

(2) If a man used the term to refer to a woman who is not, in fact, young, it would be understood that the man is playfully pretending to be mistaken about the woman’s age, and thereby complimenting the woman on her youthful appearance. This would be understood even if the term is so used in passing, in the midst of a conversation about something entirely different.

(3) The woman would welcome the compliment, even if she is only a casual acquaintance of the man.

The first condition is easy to deal with. Obviously, as has already been pointed out in the comments, one term that has that meaning is young woman. Some people may prefer young lady. The term girl which was, until a few decades ago, widely used in a broad sense that included young women, continues to be so used in some settings. The term lass, featured in another answer on this page is also available, as its use in the works of literature and films has made it familiar to English speakers outside its native region.

It is (2) and (3) that pose problems for the OP. In many present-day English-speaking societies, compliments of that sort are not as common as they may be elsewhere, so it is quite possible that the woman will not understand the point of referring to her as a young woman, particularly if that is done in the context of an exchange that focuses her attention on something else. Moreover, it is possible that a woman from a present-day English-speaking society will be made uncomfortable by a remark that directs attention to her appearance, when it comes from a relative stranger, even if she understands that it was intended as a compliment.

It is also possible that an English-speaking woman would receive the compliment that the OP would make by referring to her as a young woman in the same way as his Israeli acquaintance. The risk of the compliment being misunderstood or backfiring would, however, be much greater.

What is important to appreciate, for the purposes of this site, however, is that this is not due to English language lacking the resources for making such compliments, but rather to the cultural background against which the intended compliments are made and received. The OP's problem is not that he doesn't know the correct word to accomplish his purpose, but that the cultural background of many English-speaking societies makes that purpose itself problematic, regardless of what words are used to accomplish it. Further analysis of that cultural background would, however, be outside the scope of this site.

To see that this is not a matter of language, imagine, for a moment, that the conversation that the OP describes had been, for some reason, conducted in English but with the same participants: chances are that the compliment would have been received the same way as in Hebrew. On the other hand, if the conversation had been conducted in Hebrew but the woman in question were a visitor from the United States who learnt some Hebrew, it is quite possible that she wouldn’t understand the compliment or would be unsure how to take it.