That in a nutshell is a problem with the patriarchy and feminism. You cannot on the one hand argue that women are strong independent adults capable of controlling their own destiny, but on the other hand argue to remove their agency when it suits and hold men responsible. Women either are strong independent adults - in which case they need to learn to live with the (sometimes negative) consequences of poor decision making, or they aren't in which case the entire notion of feminism falls down.

This picking and choosing when women are agents of destiny and when they're delicate little flowers needing the protection of men (and other older wiser women) is one of the biggest contradictions holding feminism back.

1. Is she an adult?

2. If she has told you what she wants from you, she has given consent. Your obligations to help stop there.

3. If she is mistaken/doesn't understand the implications that is her problem. She may regret it, her regret is not your responsibility to perceive.

That may sound harsh on first reading, but it is what equality looks like - it treats both sexes fairly and equally. Her holding you responsible for her own poor decision making - which MAY have happened in the case of Gaiman (it also may not) is not a direction in which society should travel. It will simultaneously disempower women and turn men against them.

I'd argue this is already starting to happen.