We all know that sex makes babies. So when you have sex this is the risk YOU take. This is YOUR responsibility...the onus is on YOU to make sure that pregnancy doesn't. If you don't want to be a parent yet then there are things YOU need to do. It's wrong for this woman to want to try and trick this man...but it's equally wrong that this man isn't taking the initiative in protecting himself. The same if it were reversed.
I think the ONLY time when the responsibility is primarily on the 'tricker' is if they tampered with the person's contraception. So if someone poked holes in condoms or swapped the pills and made them all sugar pills or something or other.