There's this person I know who complained behind my back that I snubbed them. Do you think I should talk to them?
Well, what did they say about you?
I really don't know, to be honest. I'm trying to avoid the situation.
Even if they complained about you in the past, you should reach out to them. It might escalate the situation and the relationship might become unsalvageable.
I have to know what her problem is before I do anything.
It seems the best way to find out what their problem is is to ask them. Clearing the air will help resolve the issue, one way or another.