Good descriptions!
I don't think this is a calcium/diet deficiency,
especially if it's just one bird that has an issue,
but rather a shell gland glitch.
The prior prolapse might slant towards her having anatomical anomalies.
It may always be there, or get worse, or get better.
Only time will...
How do the shells feel when you break them to eat?
Are they hard all over or are those marked spots thinner?
Can you see those marks on the inside of the shell?