I think today events need to learn a thing or two and im guessing Henry wife passed away rip. Martha handle her lost love so maturely and a good example for how people should act
it's also been a good 30 years (probably 50) since she had to come to terms with it. She did mention a lot of time passed in her explanation to Becky (and she did cry while performing on the stage). Based on Martha's narrative (and if they indeed are both at Henry's wife's grave which I agree with), it seems like she even befriended Henry's wife
Also, she wouldn't have been able to lecture Becky about the homewrecker thing if she did the same (adultery often backfires for all involved parties).