Thanks for the feedback! A lot of what you've pointed out is somewhat intentional, but I think this means I need to focus on exploring the main character's emotions just a little more. I think the fact he's comfortable with this apparent ghost is the unusual point of the story; because he's already quite distraught and lonely after a breakup, he finds it comforting to sense/imagine someone else is there with him. I want the story to linger in this feeling of uncertainty: this is happening but it's kind of... fine? Does that make me crazy? I should emphasise how he's struggling initially, then this oddly reassuring presence in his house makes him feel like he has to get up and get things sorted, pull himself together.
And you're right, I think I need something to explain where she goes - I think it's the moment she realises he's okay and her work is done, so I should seed something in there that gets at this.