The best inference that can be made about Letty based on the given passage is:
A. Letty doesn't make a lot of money waitressing.
This can be inferred from the line "Early customers didn't normally tip very well" which suggests that Letty's income as a waitress is not very high. Additionally, the fact that Letty has to work two jobs - waitressing and working at a factory - indicates that she needs to work hard to make ends meet.