Yep you do get skirts that tight, and on the whole they are not stretchy, so a high stretch resistance, even up to 980 is required, unless the skirt is jersey or lycra in which case you would have a lower stretch resistance but a higher Stretch Damping.

If you want the chair to interact, which you would here probably, make sure that when she is sat, her buttocks don't go below the seat of the chair (I usually flatten the buttocks and depress the seat of the chair with the morph brush. Same applies to her thighs and shins. I would then make sure that such morphs are zero on frame 1 but set on frame 30 (the chair can have the morph throughout.) I would then copy her position from frame 30 to frame 1 so that there is no vertical movement during the sim. I would move the chair back and down on frame 1 so that it moves up into the figure rather than the figure moving down to the chair (much less energy entering the simulation that way) If you are just simulating the skirt (hip in the cloth) then for that skirt you would need to add hips, (possibly addomen) rThigh, lThigh, rShin, lShin to the collision objects and use a low (0.1 to 0.2) offset and depth