I took out my mother's 2.5 yr old locks in the summer using the conditioner+oil method. We used EVOO and Cantu Shea Butter Leave In. Lots of it, until foamy and slipper and gunky. I chose the Canrtu because it had protein in it.
If I could take out her dreads, which a stubborn and arrogant stylist had sister locked in some spots, you should be able to make it work if you listen to everyone's suggestions. Good luck.
Have her clarify too, I think? Make sure all shed hairs are out, first. I imagine with the 10 months of dirt, and all the conditioners and oils added, she will need a goooood strong shampoo.
I used the stick of a rat tail comb to pull a loop into each lock, or pull pieces out (they would come out in clumps of coils, but be tangled) then take the teeth and very slowly and patiently detangle bottom to top. Once I made it to the top I had to do it a few more times for each lock, or section the clump of hair and repeat, because there were a lot of shed hairs. to keep her hair from tangling and too keep track, I double strand twisted each (former) lock once I was done.
If she does not need to make public appearances, I also agree that you should have her sleep with the conditioner and a lot of oil in overnight. They key is slip, and then it isn't too bad.
I can't imagine the dirt, though. But again, good luck.
