I would like to know how much it will to bring my girlfriend from london to usa. How much for passport and visa

If she is a British citizen, she can enter US on a visa waiver program (visa upon arrival/no visa fee) for 90 days. If she is not, but lives in UK, visa fee is $131.

Be careful... check IP from her email address to make sure that the mails were sent from UK and she is not a scammer because a lot of Nigerian and Ghana scams also claim they're in UK.