I might get flamed for this but I wouldn't actually call it MultiTasking. to me it's more like "look at me, i'm so busy that I don't have time to eat lunch *and* get a pedi so i'm doing them at the same time. oh, and i may whip out my phone at the same time and discuss MyBigProblems cause otherwise i just don't have time".
Unless she has some pressing medical issue, she doesn't have to have a pedicure, or eat McD's. if she really needs to eat, she should eat. if she doesn't have time to do both, then she should choose what's more important to her. like the rest of us do. I *don't* use my commute time to make loud and annoying phone calls, nor would i bring my lunch into a nail salon. Especially not a McD lunch which smells, and drips and... Personally I wouldn't bring a coffee in either, because I don't want to drink chemical residues that are in the air (bad enough I have to breath 'em), but I think a covered cup of coffee, maybe a small cookie is fine. A whole meal? seems inappropriate to me