Unless you have 'I am a punter' tattooed on your forehead, I wouldn't worry about it. Assuming this happened when you met Alexa, per your review, I am pretty sure her neighbours are not aware of what she gets up to. She seemed pretty cautious about that when I met her.
Remember that you could be a family member visiting, or a plumber, or cable TV, or anything. Unless a flat is known to be a brothel (hers isn't), no-one will suspect.