Yes this happened to my best friend actually she is a step mum.
I'm sure the reason that the daughter wouldnt use them was denial;because the start of menses highlights many issues for them. All my girlfriend did was have a couple of talks with her to no avail and the birth mother did the same because she wouldnt use them at her house either. My girlfriend would find wrecked undies underbeds and stuffed in the back of wardrobes. My girlfriend just made sure there were pads everywhere. some in her bag discreetly, some in the toilet and some in the bathroom and some in her bedroom. eventually after a few cycles she succumbed and started using them,whether its because it was a natural progression or one of her peers at school advised her though i'm not sure. Maybe its just one of those gently gently issues. I personally dont think i would have the heart to make her wash her own clothes because if she is having trouble proccesing puberty i would think this might further heighten her embarrassment(only a guess),but she really is just a kid and i would think it would gross her out.As mums we tend to see and clean and do everything so for us it really isnt a big issue. A gross issue but for us mummys its just another chore. I previously used cloth sanitary napkins and hand washing is gross but it is a lot more funky and comfortable then disposable products but that again is just my own personal experience. my own daughter is 8 and she admires mummys pad stash as they are in her words cool-and yes i've had indepth talks with both my kids about everything from lactating to birth to sex to ejaculation to wet dreams and voice changes and pimples and hormones,and safe sex and bras and periods and mood swings. i think i covered all the bases without terryfying them. They are very interested in all the human body can do. As much as i dreaded these coversations they were all very gradual and very easy. I guess i have very QUICK kids that i didnt need to go over things constantly. But often i'll get the private one liner,like my son saying as he walks into the toilet"oh mum youve got your period!" "Does your tummy or back hurt?"I think he is great partner material for his dream girl when he gets older. Mr emapthy.