Not to say she will be offended
Given that pretty much the entire point of Lilly's happy ending is that you have to *avoid* taking advantage of her blindness and/or abusing her trust (i.e. not hide information from her), I'd have to say she might very well be offended. Blind people can be *very* vulnerable in certain ways, and if this person you liked kept taking advantage of your blind spot (so to speak), don't you think you'd begin to not trust them after a while?
Then again, there are some seriously twisted and wrong possibilities if you actually went through with it...
I'm surprised nobody's mentioned the Family Guy episode "The Blind Side" yet. The whole 'A' plot involves Brian dating a blind girl...who just so happens to hate dogs.

Realizing that he's already comitting a pretty big lie of omission by not telling her his actual species, he proceeds to take advantage of her even further -
creating a variety of staged scenarios to impress her with false bravery and generosity. Not exactly *mean*, but most definitely grade-A manipulative bastard material.

The biggest deception of all comes at the very end of the episode, after she finds out he's been lying and dumps him - he ends up dating her *again* by simply doing a different voice and pretending to be a completely new suitor.
I'm starting to understand why Quagmire hates him.
