“women certainly have more of a specific obligation to keep it, differently from men. To be clearer, I should just have pointed out that generally we are taught from childhood that those are the big three for women”
Technically, for those three mitzvot the obligation is identical for men and women. The very, very strong minhag is that women light the Shabat candles in all Jewish homes. Someone has to take challah from any bread that is baked that is greater than a certain amount and since in most homes, it is the woman who does the baking, it is the woman who takes the challah. (In commercial bakeries men often take the challah.) A woman is trusted to tell her husband whether or not she is niddah and whether she has gone to the mikveh, so the way taharat hamishpacha works in practice the woman is responsible.
The source for these being considered “women’s mitzvot” is a mishnah in tractate Shabat that is read every Friday night in most Ashkenazic synagogues, part of the “Bamei Madlikin” chapter.
You can find it in any Nusach Ashkenaz Shabat siddur.
(I should add that I have no desire to change any of these minhagim; but we should be precise in our exposition of halachah. Personally, we never bake enough bread to require taking challah, and I only light candles when traveling out of town, or when my wife, a physician, is busy saving someone’s life as Shabat comes in.)