character. Apart from anything else, given Avon's observed low tolerance for what he sees as unintelligent behaviour, it is hard to believe that he would ever have felt affection for a fluff-headed female who gushes over him -- but one can't place too much weight on that, since men have been known to be susceptible to the most unlikely love-objects.
However, in previous scenes Sula has come across as highly competent, intelligent, ruthless, cynical and sharply articulate -- one might almost see her as a female counterpart to Avon. She herself says "We were well matched." I'd guess that she, too, is accustomed to thinking of herself as emotionally invulnerable; that Avon found a weak point in her armour that she has long since believed to have hardened over again. I assumed that when she comes looking for Servalan and out of the blue finds Avon -- and however intellectually sure of success she may have been, she must have been running a pretty high charge of emotional adrenalin in any case at this point, poised as she is on the brink of pulling off a successful coup -- I think she panics, fatally.
I see her actions as a textbook example of guilty behaviour. Even if she still loves him -- especially if she still loves him -- she is in an absolutely impossible position. Instinctively she tries to throw up a smokescreen; to distract him physically and emotionally, by embraces and demands; to give him no time to question the version of events he had been fed, that he had always believed.
Imagine a child caught unexpectedly with some forbidden item in her room. She jumps up and rushes to put herself between her mother and the evidence, chatters loudly and too fast, tries to catch the mother's gaze, drawing attention to herself and away from the prohibited object. It's instinctive -- and the mother, of course, at once knows that something is up because the behaviour is so unnatural.
I assume that the Anna Avon used to know would never normally have behaved like that in public, or even in private. I think her very desperation tips off Avon that something is wrong.
In a way, Avon possibly gets less of an emotional shock when they meet -- after all, he's been thinking about Anna almost constantly over the last few days, even if he does believe her dead, while we can be pretty certain in the light of her recent priorities that the thought of Avon has taken her totally unawares. Emotional turmoil in Avon does seem to manifest itself in degrees of weirdly passive shut-down, as witness his behaviour after killing Blake and his actions with Servalan in a few minutes' time after Anna's death; but I'm not sure that's what we're seeing at this point.
Behind the apparently numb facade, Avon's mind is evidently racing away, analysing the unbelievable as he stares at her. He is wary and taken aback, first by her apparent resurrection and then by her off-balance behaviour. He knows something is wrong almost from the start.
By the time the masks are off at last, it is far too late for a lovers' parting. But as Avon himself recognises, in trying to kill him she is more 'honest' -- more the clear-headed, resolute woman he must have known -- than in all her over-urgent protestations earlier.