I think it's up to interpretation. Was coughing boy always the stalker and the girl was mistaken/ponytail was telling the truth, or was it ponytail before and something about seeing the two leave together made coughing boy follow her, either to try and protect or he thought ponytail's method worked?

I believe that's the intended effect. It makes the characters feel more complex and real, like real people.

It's wonderful seeing new art from you, even your rusty art is adorable! I have also been shaking the rust off my drawing skills, did a whole month of Inktober for the first time ever last month (I always fell off it before). It's a struggle as you said, but it's worth trying ^_^