"I am a woman, you know."
女ですよ。can hardly be uttered without context, and is a very confusing sentence for beginners.
Depending on the context, 女ですよ。could perhaps be translated into some of these:
男と女でどちらのほうがXか知っていますか？女ですよ。- Do you know which sex is more X? Females. (btw please always be sceptical about the scientificality of statements that follow this format)
ニヤニヤしているから分かります。女ですよ。- I can tell by the smirk. There's a woman he's into.
あなたは女ですか？ー女ですよ。- Are you a woman? -Yes, I am.
If I were to translate "I am a woman, you know." I would take わたしが女だということを分かっていますか。- (literally) Are you aware that I am a woman?
I am not japanese, but i have read in almost all my japanese books, when they talk about ending particles, that よ is mostly used by men and that women use わ instead. Thus, maybe my books are wrong or it has changed recently in japan, but if they are right then this sentence could hardly be heard in Japan and a woman should certainly say "女ですわ" and a man would say "男ですよ". Does a native japanese may explain if I am wrong or not...
If I remember correctly, Misa Sensei said that よ is informational. It is stating something known. I think this is why duolingo translates it as, "you know".
I have heard and read the same as you, that よ is stronger and generally used by men. However, in my experience in Tokyo, Japan, both of my host sisters (ages 5 and 13 then) used よ in their daily conversation. So, I think that it may just depend on which part of Japan you are in and what setting. At work, I think you need to be more formal, so you may not use it there.