Not 海伦, but I don't think your question is ethical

1) you don't have a choice if you commit to do anything. Otherwise, don't commit.
2) if you're a professor, you should not date your student.
3) if you're married, you should not jeopadize your marriage.
4) if you have children, you should not challenge their respect for you.

Period. I bet Helen would say the same thing with me.

If you really want her, wait till the "teacher-student" type of relation is over.

Wanna play? play within the rules.