Relationships can serve many different purposes. It could be that this young woman values your contributions in the club and finds you intellectually stimulating in a way that she doesn’t get from other people. It could be that she sees you as a “little brother”, not in a dismissive way but as someone younger she wants to encourage and mentor. Or your confusion could be a result of your personality differences. As you know, INFPs tend to be passionate about whatever they are excited about. She may not know how to show that interest without being confusing. Meanwhile, INTJs tend to be overly analytical. So you may be over-thinking this whole thing.
The most direct way to figure it out is to ask her. Yes, I know. That’s hard to do. But surely it is no more difficult than being confused about what she means and what she wants from you.
Just keep it light. You might find a private moment and say something like, “I really admire how much you bring to our club and I’m glad to be your friend. But sometimes I find how you treat me a little confusing, especially since you are a senior.” Then be willing to listen. See where it goes. I have a guess that she doesn’t have any idea that she is making you uncomfortable. Be prepared to reassure her that you aren’t looking for romance; that you just want to better understand what she has in mind.
You have another half year of school before she graduates. You’d probably like that time to be as comfortable as possible. Good communication is the route to being easy with each other.
I wish you well.