I think that its related more to when the baby decides to give up... as apposed to what you can do to increase the milk supply... Obviously when there was enough milk there the baby still preferred bottles over the breast...
The woman's body produces milk when it is in need of supply. If the baby is not drinking the milk, then the body is told to stop producing milk supply.
Perhaps the baby isn't breastfeeding enough to keep on producing milk. However, some woman just can not beast feed well, whilst others can go on for long periods. Theres nothing wrong with that, its just nature. In the end the baby will be fine, as there are good formulas out there nowadays to supplement it.
Perhaps the baby just preferred the bottle over the breast, as maybe the breast wasn't enforced enough. So then maybe become more comfortable with the bottle.
How many months is the baby now...?
I breast fed my son until he was 13 months, I wanted to stop at 10 months at the most, but I gave him the time needed to be ready. He hated bottles, though I only introduced him to bottles at 4 and a half months. I think its best to only give them breast and not be made aware of bottles till there comfortable with the breast. Then introduce new things.
I new plenty of mothers, who gave up trying on the breast cause 'they' found it too hard, so they gave up and gave them bottles.
You just have to concentrate on what the baby is telling you, of what they need...And to not get too weak on them..