Last Resort Technique - Can I correct problems?

[LostIn407]

I can't not respond to the text. I don't even do that to people I don't like.

I think I need to go over boundaries with her.
Option #1:
Send her this text:
"I cannot go to a movie with you. It gives me a false sense of hope. As long as you continue to see OM, I cannot spend time alone with you."

Option #2:
Decline the movie but offer to meet her for a drink after my plans. At this time, I will tell her that I do not want to be her Plan B any longer and I think we should stop any further interactions until OM is gone.

Option #3:
Simply text her I have plans until 11 and can't make the movie.