Illun

Some thoughts on continuing it:

It'd be a pretty dull ending if she stayed like that and nobody ever found her, so that might be where to start. A landlord, boyfriend, husband or burger would be the most plausible ones to do so.

From there, you could either have the newcomer handle her, help her find a cure, or make the mistake of looking inside the washer where the sludge wound up and getting shrunk themselves.

If you decide you want her to be cured, you could have the heat applied in the drier cause the sludge still on her outfit reverse it's effects, again while catalyzed by stimulus as the shrinking process seems to have been. It could also wear off gradually or have someone develop a cure for her.

Going a completely different route, you could do something like Kumiko where the effect is temporary and returns again when activated by vibration, sex, electromagnetism (the motor), constraint (the weight of clothes on her shoulders), etc.

My favorite concept out of those is the idea that her body now shrinks in response to constraint, down to a minimum level, such as her current size. That would mean she would be able to stay normal size as long as she's naked, and that anyone wanting to keep her small would simply have to tie a string around her somewhere and she'd be stuck small until she managed to get it off. You could have some particularly light dress that she manages to wear and then let her friends take advantage of her dilemma for all sorts of little fun.

One last thought would be that it endows her with powers akin to Shrinking Violet - either the power to shrink and grow herself at will, or to shrink anyone around her at will. It might be interesting if she could shrink/grow anyone but herself.