(Hadley Hooper/for The Washington Post)

Q. My 12-year-old stepdaughter is well into puberty, but she avoids baths and showers. She winces if someone gives the slightest tug to her thick and beautiful hair, and she says it hurts if someone brushes her hair or styles it.

These problems have gone on for years, so she styles her own hair and has always bathed and showered herself, too. But not very well.

I thought that peer pressure or vanity would help her get over this problem, but time hasn’t helped. My stepdaughter has told us that she waits several days to bathe at her mother’s house, where she lives most of the time, and that she doesn’t change her underwear from one shower to the next. When we see her, which happens once a week and every other weekend, she often tells us that she hasn’t bathed since we saw her last.

Her mom thinks that this is just a phase and has jokingly told us she has “given up” on getting her daughter to brush her hair and, presumably, to bathe.

At our house, we simply tell her that it’s “shower time,” but she still avoids the issue and promises to take one later. When she does shower, her hair seldom looks or smells clean, so we finally asked her to show us how she washes it. It turns out that she barely touches her hair and never works her fingers all the way to the scalp.

My stepdaughter is so beautiful, but her unbrushed hair makes her look raggedy, and she’s somewhat smelly. Yet she likes to swim, and if we can get her in the bathtub, she doesn’t want to get out!

Nagging doesn’t work, plus it embarrasses her. But what else can we do?

A. Hygiene really starts to matter after menstruation begins because that’s when the sweat glands go into high gear. Unfortunately, it usually takes a year or two for a preteen or even a young teen to realize that she smells like a goat. Children may approve of Godliness, but Cleanliness? Not so much.

It’s true that an 11-year-old will usually wash her face without being told, but she may not see any reason to wash the back of her neck, even if you tell her it is as gray as her sweatshirt. And if you ask her to use deodorant, she might either forget what you said or spray her shirt with Febreze and think that this is enough. Your stepdaughter is simply at an age when she doesn’t think she smells as bad or looks as raggedy as you think she does.

Since she has always said that it hurts to brush her hair, however, she may have sensory processing disorder, because many sensory receptors are in the skin. If that’s the case, the drops that fall from a shower head could feel like sharp little darts to her, and the brush that someone pulls through her hair may truly hurt her scalp.

Occupational therapy can get rid of these sensory problems, but if these are her only signs of sensory processing disorder, you’ll probably find that bribery is quicker, cheaper and kinder. Just don’t ask this beautiful child if she took a shower recently or when she changed her underwear. The embarrassment that these questions might cause could lead to a serious estrangement between you when she’s a little older, for hygiene is an intensely personal choice.

Your stepdaughter does need an occasional reminder to clean up her act, of course, but it would be better if you said “bath time” rather than “shower time,” because she prefers a bath. Give her bubble bath to lure her into the tub, conditioner to make it easier to brush her hair, deodorant to keep the goatish smell away and a few pairs of cute panties so she will want to change them more often.

You also might treat your stepdaughter to an occasional manicure, but choose a salon where there’s a stylist who likes young people and who would be willing to teach her some pain-free ways to wash and brush her hair. In time she may let the stylist thin her hair so it will be easier to comb and may even assent to a full haircut with a shampoo and blow-dry eventually. She’ll complain all the while, of course, but vanity should triumph when she decides to grow up, which will probably happen in a year or so.

Questions? Send them to advice@margueritekelly.com.

Read a transcript of a recent online Q&A hosted by Marguerite Kelly. Her next live chat is scheduled for Feb. 23.