demolitionman65:
…is now accusing my wife of being immodest because she wears pants on occasion. To my mind, this is excessive, but it did lead to the question of “how much is too much?”
I think it is more important to look feminine and modest rather than condemning pants outright. Fit and cut (not too tight, too revealing) are much more important, in my opinion, than the fact that they are “pants.” Someone pointed out on another thread about modesty once that St. Gianna wore pants, so if it was a complete bar to holiness I think the Vatican would have noted that.

That being said, dresses/skirts for women are more appropriate and especially so for certain situations, like Mass.
A woman should ask herself: Do I not wear a dress because I don’t want to look feminine? If a woman is rejecting traditional feminine appearance on philosophical grounds, that would be a cause for worry.
Likewise, someone who can’t be bothered (male or female) to regularly take some care in how they appear in public would be a cause of concern. Like the fellow who always appears in sweatpants at Mass, despite the fact that he wears business suits to work all week, because he just feels “more at home” that way (or some other excuse). Obviously that’s very different than the person who wears sweatpants because that’s all they have in their closet, or all that fits!
Some Catholics do try to define very rigidly what is acceptable clothing for women. Dresses only, knee-length or longer, sleeves at least 3/4 length, and so on. I have seen a website that says that we shouldn’t wear anything the Virgin Mary wouldn’t wear and that we can see what she’d wear by how she appears in traditional art and approved apparitions. There is a certain appeal to this argument and I think you have to decide for yourself whether you agree with it.
I have tried the dresses & skirts-only thing before and found it very difficult to maintain. I had few clothing options from my local stores that were practical for every day life. I do wear skirts only to Mass about 99% of the time (the 1% being when I forget to do laundry in time) because I feel it is more appropriate and sets a good example for my daughters and other children.
I think you can be a good Catholic and disagree on this issue of whether women should wear pants or not. Femininity and modesty are the more important virtues to cultivate.