I know a lot of people are interested in the coach, but I think it will still be a while. For most people the MC is dating her daughter and she knows this so that is a barrier for her. Then you have the Coach and Player conflict as well. Both of these are going to take time for her to get over before she is willing to take a chance. There have been several actions to show that things are moving in the right direction (the MC stood up for her to Charles to save her job, he saved her from getting hit in the face with the bat and was ok with being left out of the game coming up), but we need to keep in mind she is focused on trying to win a game and keep her daughter safe. She clearly stated in the last update her goals are to see her daughter get married/start a family and to win a game. Starting a romance with the MC potentially gets in the way of both of those things. We are probably going to have to wait a while longer before anything happens between them.
I think the walls preventing her from taking action are slowly coming down, but I feel we need two things to happen before she/MC takes action. First there needs to be more movement on the Natalie and MC dating, and second the team needs to win a real game not a scrimmage game or a preseason game but an actual game that counts. I think that when the MC and Natalie finally have sex that Harper is going to walk in on them or see it happening. This will cause her to be more interested in the MC as she will want to experience that too. I also feel that we need to learn more about Natalie's kidnapping attempt when she was younger, as I think that is going to play into this as well. Then the team needs to win a game based on the heroics of the MC. Once that happens I think she will kiss the MC and then everything will progress quickly after that.
For now we just need to wait until BD feels it is the right time to add lewd content for Harper. There isn't a magic path to take to make this process speed up. Trust me once there is content we all will know as she is one of the most popular characters here. She ranked number 4 on the rankings we did back in December with her daughter at number 5.