Sorry, Sayaka. It may have started out with you asking for the skirt so you could iron it or whatever, but kissing while you rub her naked thigh pushes the boundary of "this is perfectly innocent, I'm just being her mother" a bit too far for believability.
At this rate it won't be long before they're just having sex while Sayaka desperately tries to find some way to justify it as something perfecty innocent and motherly.