Co-worker has been secretly building a case against me to HR

I've just found out that a coworker has been rallying others and attempting to build a case against me to HR and management because i'm too quiet when i'm around her and others and it makes them feel uncomfortable? Mind you, I do keep to myself but this somehow bothers her considerably. I don't try to fraternize with coworkers too much, as i've learned it can be detrimental as they can use relationships against you. I've never encountered such drama, at a job before. I actually feel like i'm back in high school all over again with people who are considered adults. Also, the coworker that is doing all this behind my back is a female. Just wondering what steps I can take to navigate through this?