Speaking as a female, I can tell you: A husband almost always knows when his wife is having a period - she doesn't act any differently, but she doesn't have to tell him, for him to know. How could he not know? - they live together and they sleep together.
Most husbands have the occasion to buy pads or tampons for their wife - at least once in a while. You might be going to the store, and she'll say, "Pick me up a box of Tampax while you're in there".
You don't have to do anything to "make her feel better during this time". Make her feel better? She's not sick - she's just having a period, and she feels okay.