yeah, but I don't go into overdrive and am not critical during PMS... so I'm not sure I have good advice for you there. But, my advice about dealing with someone who is consistently (during PMS) critical and difficult is to think long and hard about whether the friendship is worth the maintenance. Your first responsibility is to be true to yourself -- and that means not walking on eggshells.

If you don't want to say sayonara to her altogether, then what about telling her that there are times when she's difficult and that hopefully she'll understand that you don't want to spend time with her when she's in that kind of mood.

Or, you could give her the feedback that you find her unpleasant to be around once a month. Maybe she'll thank you for it. You could offer to be her check-in friend, so that if she's not sure if her mood has changed, you could let her know so that she either works to overcome it, or else avoids people until her mood passes. You'd be doing her a favor, IMO.