I was fired after taking a leave of absence for a mental health condition, and am unsure if my employer had the right to terminate me.

I took a leave of absence to seek help for a mental health condition. I was seeing a counselor, and was assured by Human Resources Representative that even though my counselor wasn't a doctor, she was still able to to fill out my FMLA paperwork, and turn it back into HR. My doctor didn't meet the deadline that the paper work was due by, so I was given a 7 day extension. On the seventh day, I got a phone call from my counselor saying that she had spoken to my HR Representative, and was told that she wasn't allowed to fill out the paperwork, though both me and my counselor were told multiple times until this point that she was allowed. One or two days later, I received a letter in the mail saying that I have been terminated. Is this legal? It seems as though my HR Representative is either not sufficiently informed about the rules of FMLA, or she knowingly gave false information in regards to who I should have fill out the paperwork.