What are your collision settings? From the rim of your skirt it looks like the skirt's polygons are rather large. The default collision option (in "Simulation settings") is "cloth vertex against object polygon", but this is only good for a (relative) high-poly cloth against a low-poly figure. If you have a higher-poly collider, you have to use the "object vertex against cloth polygon", too. And if you have outstanding edges (like the 90deg-angles in your chair, or the rim of your skirt) in your collision, you should use the "polygon against polygon" option.

Also note, that when setting your character on the chair, there should be enough space between the chair and the thigh for two collision offsets (one in direction of the thigh and on for the chair), so that the cloth can levitate freely between. Otherwise the cloth-simulator does not know in which direction to move and the result is basically random.