I plan on getting my girlfriend sick 6 days before she has an audition.
You want to intentionally sicken your girlfriend?
It's not that I want to get her sick, but I think she'd have a better chance to get into this class if she was petite.
Seems like you're trying to get your girlfriend thin through an illness. That seems like it's going to be very detrimental to her health.
I know I just don't see her as thin/fit.
It seems like you're really worried about her weight, but for all the wrong reasons. Intentionally getting her sick to lose this weight could have some long-lasting health problems. If you believe her to be an unhealthy weight you should talk to her about dieting.