It's not strange though is it? She was completely traumatised. She's just seen someone in her house, absolutely paralysed with fear, all she can do is lock herself in her room and hope nobody hurts her.
Or, she's in a party house. She doesn't know what's going on, people are in and out all the time. She assumes it's just someone who's come to see one of her friends, some weirdo who always wears a mask.
Neither of those scenarios point to anything strange. They point to a poor young woman who will cope with immense survivor's guilt for the rest of her life, and even worse, she's doing it when the whole of social media seems to think she's someone evil.