That's what bi-bi advoctes say every single day. If you don't learn a soild language in young childhood you will be critically handicapped and unable to ever learn fluent language. That is why they insist that ASL is the only choice for young deaf children.
If these adults did not have access to ASL from the start then it shows that ASL can be learned at a later date with great fluency. If they did have ASL from the start, why didn't they learn to read and write? I thought having ASL as your first language makes English acquisition easy??
I assume that the school she went to school that was TC and she only know ASL . Most school of the deaf back then were oralism (but the kids were more bi-bi because they were signing to each other.. and get their hands slapped) later SEE/PSE/TC at least that's what I reading from deaf school histories.. and that school today had lower expectation of writing. Which why we feel that deaf school should strengthen literacy.