I've had to skim some answers, so sorry if I repeat.
Someone else suggested the coated hair elastics to reduce hair breakage. And I firmly agree - buy them in bulk.
But here's another option - find a good quality hat elastic, buy a good supply of it then cut it into the right lengths for her hair. Allow an extra bit of length to tie a reef knot in it, to make the loop.
easy child 2/difficult child 2's exBF (we were only talking about him last night) has long, very frizzy (AA-type) auburn hair. And he had no idea how to manage it. My daughter would spend hours, literally, combing out the knots and dreadlocks which would form. It was so think it wouldn't wet. In the rain the water would bead on his hair then drip off. He had to use a lot of shampoo just to break the surface tension.
We tried just about every product you could think of, but what did the trick in the end was oil.
Now, it doesn't have to be baby oil. You can use cold-pressed almond oil which also doubles as a deep conditioner for the hair AND the scalp. AND she can perfume it with whatever she chooses.
Because we're technically, geographically, part of Asia, we may have access to products you can't get. But this still could be duplicated, if you can't get it.
We get a deodorised coconut oil which is perfumed. It comes from Fiji and they use it there on their skin and on their hair, to tame the frizz. There are three fragrances - rose, tiara (which smells like jasmine, the picture on the bottle looks like star jasmine) and sandalwood (clearly for the boys). This is pure stuff, it's inexpensive. It solidifies below about 28C, but you can scoop it out solid and it melts almost immediately on your hands. Smells and feels wonderful.
Braiding DOES hurt. A friend of ours is a professional singer, had her hair braided for a gig and ended up missing the gig because it brought on a migraine. But if she tried with a friend, maybe, larger braids done more softly shouldn't hurt as much. They don't last as long either, but they can give a different look.
easy child 2/difficult child 2's current boyfriend has frizzy hair but not like ex-boyfriend. He's wearing a lot of scarves and going through a lot of gel. Scarves are good, for taming the bouffant look. Bandannas, turbans, all sorts of fabulous stuff you can personalise.
As for difficult child - you've had some good suggestions. What has worked for us - the sniff test and making him re-shower is a good one. An absolutely brilliant antiperspirant is also needed. They have to put it on after each shower, and each morning. Find one that he is OK about using - roll-ons can snag in underarm hair, stick deodorants can leave chunks caught in hair. He may insist on a spray-on. It's worth the expense.
Next step - you do not put smelly clothes on a clean body because if you do, you just wasted the wash. So first step for him, always, is to sniff his own clothes before he puts them on (or get you to sniff, to make sure).
Clothes that smell should be walked straight to the laundry and immediately have white vinegar splashed onto the smelly area. They then go into the "to be done" laundry basket. If they're really bad, they may need a pre-soak as well. But you would be amazed at what just a splash of vinegar can do.
Some clothes will retain a BO smell even right off the clothes line, so if the vinegar treatment doesn't work on those, throw them away. because even straight from a thorough wash, he will smell of BO within minutes of putting these on - his body heat releases the dormant BO smell.
Washing clothes - experiment to see what he likes, but you may need to use a good quality fabric softener. Also, experiment to find what fabrics he prefers.
A problem I STILL have with difficult child 3 - he likes his clothes to smell familiar. We've finally got him off clothes with strong BO smell, but there is another, purely male smell which he recognises as his own and he doesn't like it washed away. He gets cranky with me when I raid his room and wash hid linen and pyjamas. "You've washed my smell away! They don't smell right, now!"
But I pointed out that they will have that smell back within minutes of being put on his clean, deodorised body. And they do.
Keeping a pack of baby wipe-type of wet washcloths is good - I've sometimes handed one to the back of the car and said, "Clean yourself, especially the armpits. You are not getting out of this car until you smell clean!"
I'm a non-smoker with bad eyesight, which means my sense of smell is legendary in the family. I also dabble in herbs and aromatherapy, which has honed my sense of smell even more. So no kid can tell me if he's washed and get away with it if he hasn't. difficult child 3 comes out of the bathroom with wet hair - I can send him back to wash it properly, when I can smell (even through the body gel, bubble bath etc) that he hasn't. And they know it.
Maybe that's why none of my kids has taken up smoking - they know they wouldn't be able to hide it from me. I can tell if someone has just been around smokers, or has actually had a go themselves. I know if someone is a problem drinker. I even know WHAT they have been drinking.
So if my sense of smell is that sensitive, why should I think my kids aren't like that too?
Texture is also important. we've found soft t-shirt jersey is best with the boys. Sometimes they like the satiny polyester fabrics but these don't breathe. Scratchy clothing labels often have to be unpicked (never just cut them out) and often a plain cotton drill is the worst, unless it's second-hand.
If you can re-train his sense of smell to weed out the problems instead of being drawn to them, it may help. Finding a way to turn him off BO and turn him on to a healthy body smell may be a start. Girls LOVE that sexy pheromone smell of a clean, musky male. But BO masks it and kills the romance.
I hope this can help in some way.
Marg