Sheep rolls are hard on the teeth, as are turnips. Try sheep coarse mix which is easier to chew.
I think you have picked up a mixed message about pulling out teeth. When an older ewe gets a wobbly front tooth it can put her off ripping grass, so you can pull out a wobbly one, but leave the healthy teeth.
I don't know if six and a half is old for BWM but that is young for the breed I keep, Hebrideans, so I would be investigating my breeding criteria if mine were losing teeth that young. See if broken mouths are occurring in one breeding line, and only breed from ewes with good mouths, good feet, good milkiness, good udders, longevity and so on.
If they start to lose condition then give them extra coarse mix, don't breed them that year and make sure they have grass which is easy to pull, as well as lick with treacle. Watch their condition and react quickly. If it's just one tooth which is wobbly, then once that has come out they will usually start eating normally. For your ewe, she has already lost the teeth and may be ok - if she can't rip grass with the gap there then don't breed from her, or of you do then watch very carefully for twin lamb disease.