Lancelot is absolutely silent as he takes witness of this event. Of course, he knows nothing of the specifics, and it is clear this is quite a mess of a memory to have someone else view against one's will.

Although he knows it will not change the situation, he speaks to the woman as respectfully as one can particularly when still attempting to confess sincerity to a stranger.

"My apologies, my lady... for this violation of privacy to your personal memories."... Even though it's not his fault, even though he didn't really get a choice in realizing what was going on to even attempt to look away (—but, honestly, how do you look away when you're right there in the room as something such as this unfolds, anyway—).

He says it, even though he knows it really won't help one tiny bit (because it wouldn't help him, either).