Translation:Everyone is a woman.
That's an English grammar issue. "Everyone" is a singular word, referring to everybody as just ONE group, even though it means multiple people. Notice that this affects not just the verb but also the descriptor. You would say "everyone is A WOMAN", not "everyone is WOMEN". As for the verb part, "are" is the verb for plural subjects, and "is" is for single subjects. Therefore, you could only use "Everyone IS a woman."
Sorry to say. "All" is a general term, it can refer to literally anything (it may be specifically mentioned, or just implied), and also it is a numerically indeterminate noun, it can be either singular or plural when used by itself. Its number depends on the context. If there is no context, then it can be either singular or plural.
All is not used to describe people
After the school trip, the students went back to the room. So the teacher made an attendance check, but before that, she asked, "Are all here?" Easy.
But to look at it another way, when referring to non-count nouns whose quantity is referred to as "amount" instead of "number, "all" is treated as singular. For example, if you're talking about sugar (a sweetener), you say "all is sweet", not "are". If you're referring to your friends, you say "all are friendly" not "is".
"Are all here?" - sounds incorrect. It's sounds incomplete, just like "All are women". It's definitely something someone would say, but without context, it sounds wrong.
"All are women" - Are all what women? Those trees? Those people? Those cars?
"Are all here?" - This is definitely wrong, even within the context you gave. You might use it, but it's wrong. "Is everyone here" is a much better alternative.
You would know from context, As with most kanji it is best to learn the pronunciation of whole words in the context they are used in as there is no strict pattern to their readings.
ひと is the kun-yomi, the native Japanese reading that you would use when the kanji is by itself.
But this reading is also found in some common compounds:
人通り・ひとどおり pedestrian traffic
人差し指・ひとさしゆび index finger
人目・ひとめ public gaze
Another kun-yomi is り used for counting one and two people
一人・ひとり one person/alone
二人・ふたり two people
じん and にん are on-yomi, the Sino-Japanese readings usually taken when a word is in a compound.
じん is the suffix for nationalities/type of person
日本人 Japanese (person)
アメリカ人 American (person)
白人 Caucasian/white person
にん is used for the counter for people 3+
三人・さんにん three people
四人・よにん four people
五人・ごにん five people
Both of these readings are also found in other compounds
人生・じんせい human life
人種・じんしゅ race (of people)
人間 ・にんげん human
人参 ・にんじん carrot