Well if some creep would record her in a changing room, then yes. She would have reacted very badly.
But this is her nephew we're talking about. She saw him grow up. She saw him learning about women. Getting awkward with them. Yes he's no longer at the age where if he tries to spy on his aunt, people would find it funny, but still in her eyes, he's still the kid who maybe idolized her, after all she might have been the hot aunt every friend would tease him about. I won't go too much in details, but there are consequences to the spying part, and Denise will not always look at him with the same as as now "Eh... He's just a horny teen". She'll start seeing him as a man, very soon.