She says "Yes" because she's trying to maintain cover. It can't be the truth cos then Clark wouldn't get shocked. It must be a lie, then.
She says "No" because she thinks it's the truth and she'd rather tell the truth presumably saving Clark from the shock, than blow the cover. However, since she unknowingly does love him, due to their ICONIC BOND, he gets shocked anyway?
See, this episode is so fucked up already.
What we know:
Lie detector test, One lies, the other gets shocked
Lois confesses her feelings
We know Clark does get shocked in the episode.
When asked, "Do you love this man?"
She'll either say yes, or no.
If Yes, and Clark's OK, means she does love him
What kind of Love though? Relationship love, or family love? This will be left to interpretation IMHO. Or could it be her keeping the cover true?
If Clark gets shocked, well she rather keep the cover then be honest.
If she answers No, and Clark does not get shocked means she doesn't love him.
No closeness between Lois.
If No and Clark screams, then it means she does care, yet there is a negative effect.
If she does love him, but lies, she must not love him that much that would mean she would do everything to protect him. Making it not love but lust.
So really this episode is fucked up.
Either Lois; Loves Clark romantically, Love him like a brother, Lusts for him, or Doen't love him at all.
Basically when asked that question, She must say Yes, Clark must be ok, and explain what she means on how she loves him.
If anyway else, it's an Anti-Clois anvil IMHO.
As for Clark, he's already screwed of ever being at the Morality level of Iconic Superman so, I just hope he's honest.