I did it again a few months ago. For me, I have MAD tangles and BKT really helped with that issue. However, it just didn't stay in my hair for very long. I got a good 2 weeks out of it and then my hair would revert back to its normal, tangled self---no matter what products I put in my hair. It may be that my hair is too porous or I needed a stronger solution with formaldehyde...My brand was just something I got off of ebay but the more expensive Softliss (I think) brand is supposed to be good stuff. Good luck with your sister!