Is this normal for autoflowers to flower this quickly (I looked at other auto diaries, they usually flower at week 5) Is there even anything one can do to affect when it will flower? Also, how much taller should I expect her to get?
Yep thats normal. As far as I know, no you cannot affect when it flowers with a autoflower. You can expect it to get double as tall, possibly more. It depends on the strain, phenotype and other factors as well, but I personally go by about double the height.
Four weeks is more normal from my experience but 3 weeks is certainly possible. The plant will about double in size though with training you can keep the height under control.