Distephano: I thought you were dead!
Ripley 8: Yeah, I get that a lot.
[Ripley is staring at a fork.]
Vriess: Fork.
Ripley: Fuck.
Call: Jesus Christ, Jonner, what do you put in this shit? Battery acid?
Johner: Just for color.
Gediman: You are a beautiful, beautiful butterfly.
Ripley 8: So, who do I have to fuck to get off this boat?
Johner: I can get you off. Maybe not the boat, but...
Chosen answer: Well firstly the queen was probably genetically engineered, like Ripley herself. A few days might be all the time they need to have a fully grown queen created. Secondly the 8 incubated victims were only the latest batch, they had been incubating people with xenomorphs for quite a time I suspect.
lionhead
With regards to the quick growth of the alien queen, it is standard for the xenomorph in nearly every film they appear (Aliens is the only exception, the only chestburster shown in the film is quickly killed by Apone) to grow to full size in around one day. Presumably the same is true for the queen.
BaconIsMyBFF