On a 1 gallon bowl, she really needs to do daily water changes of about half the water. One gallon quickly gets fouled, especially if there is no filter and it's hard to find filters for such small containers. It's possible that doing 100% water changes and scrubbing everything may have been keeping the bowl in a constant cycle, which would mean that the ammonia and nitrites would be present (both should be 0). I'm not 100% sure, but I believe that it may cause lethargy. It's awesome that you helped her realize that scrubbing it spotless can cause problems.
My best guess is that he's too cold. Mine did that when the temp was below 76, and he perked up nicely once it got to be 78-80 degrees. In a bowl of 1 gallon, this is critical since it doesn't have enough water to keep it fairly constant. The 1 gallon of water will easily fluctuate temps and do it quickly, which can cause stress and lethargy and even death.
I know it can sometimes seem like people are jumping all over you when you are starting out, but that's because there are so many LFS who don't have the right information and are selling fish just to make a profit. We try to help everyone get started the right way for the good of the fish as well as your bank account (fishy mistakes can cost lots of money), and it can be overwhelming when you are starting out. I know from first hand experience. I did everything wrong, from the 1 gallon betta bowl to not cycling to changing 100% of water, to no heater, and the list goes on.