The holiday binge may not be enough for you to develop Plantar Fasciitis (unless you started on it as early as September and intend to keep eating till May, figuring Valentines and Mother's Day entitles you to the same feasts) but any weight gain is sure to tax your body somehow.
Stairs may suddenly rob you of breath. The same walk of a few blocks may get you clutching a stitch on your side. Your back, feet or hips may suddenly 'give' sooner. Heck, just bumping into things due to a miscalculation of space will result in bumps and bruises.
And it's true, the heavier you get, the more pain your lower body will feel. The stiletto heels certainly won't be giving you enough support as well, so that would be double whammy for your legs.
So unless you're a masochist, keep to a healthy weight. And whatever you gained over the holidays, work on losing it asap. Delaying the return on your treadmill will just make things harder (and more painful) for you.