Comments
It was an interesting short to read. It presents an everyday situation and steps it into fantasy/horror. Your logline doesn't do it justice. However, your script still needs some work.
First, it has to tell a story, not a sequence of events. This is just a sequence of events at the moment. Boy meets girl, girl has boyfriend, boy goes home and fantasizes. To be a story, it has to have some type of crisis and resolution. To be a screenplay, it has to have these elements to create drama.
Part of the difficulty is that there is a lot of dialogue. Film is mostly visual, so you need to break up that long exchange on pp. 5 & 6. A lot of the dialogue is also superficial of the "Are too"/"Am not" variety. It is here that you can show the audience. "Well if you're real pick up that book!" Either she can or can't. If she can, you create a whole level of wonder in the audience. If not, you make the audience wonder. Do you know if she is real or not? I don't ask this flippantly. She IS your driving element.
Next you mention Markus and that's it. If you aren't going to develop why Markus is critical since she appeared when he left, don't mention him. If he is, you need to make him more relevant. Was he a close friend? roommate? family member? former lover?
What is the 'story arc'? What is Helena's purpose,
really? When your story concludes, does she kill Natasha, help Sam get Natasha, etc.? The crisis you suggest is Sam wants Natasha who is already attracted to Alex. Your ending should resolve that with Helena as the vehicle.
I really like the idea of him creating this idealized woman. But to have her around for 3 months, that opens itself up to all kinds of unanswered questions. Also the dialogue at the end of 6 and start of 7 has Helena telling us what Sam feels. It is more powerful if you can show us. A memory flashback is one way to show that. A strong script balance telling with showing.
You’re lonely. The emptiness you’ve been feeling. You’ve had it for so long and know one understands you. No one knows. What you want. What you need. I’m going to change that. I’m going to make you feel whole again.
This is where you need to find a way to show us that emptiness and loneliness somehow rather than tell us. Also what a powerful hook "I'm going to change that." How? What is she capable of?
You also have us questioning his sanity. He's seen her but ignored her for three months. Suddenly he's okay with French kissing her? This rapid turnabout seems out of place unless she can control him. If she can, why didn't she before? If she can control him, what might she do to "make him whole again"?
Reading your script, I see lots of opening and opportunities you can pursue. It is good as a draft. Now you need to craft your story. While there are differing opinions about the "Three Act Model", it is a very good place to start. Once you craft the story, write the visuals then add the words. Right now you have a sequence of events, not a story. You have characters that really come across as very flat. The viewer needs to be able to connect to one of the characters. By using Helena, you can flesh out Sam. But don't just tell about him, give him life through images.
If you say "X thinks he's a loser" it's not as powerful as seeing a carload of frat boys drive by a waterfilled road and deluge X with water and he just stands there looking like a wet puppy, sigh, and walk on as others about him laugh. Now you've created a context and depth.
It's a good start with some interesting points of departure for you to develop. Good luck.