Yes, you can get arrested for botnet if it is found to have been used for malicious activity..
There's no way to answer this question - it all depends on the circumstances surrounding why you would be arrested AND why she would be there with you.
Because you do something bad and it can be against the law.
speeding, running a light, murder, illegal drug selling, robbing, 5 finger discount etc..
a large number of compromised computers that are used to create and send spam or viruses.
sell weed, beat someone, slap a cop, kill someone, and do something completely stupid.