Heaven of course!
A heretic is someone who believes or teaches something that goes against accepted or official beliefs. Let us reason for a bit. Catholics believe Mary was born without sin. I believe the Scriptures where the Holy Spirit says all have sinned, even Mary.
Which makes me a heretic. Does this mean i now will spend Eternity in the Lake of Fire?
Another way to look at this, if i believe just the opposite of what you believe then that makes me a heretic?
You are very unclear. You have muddied the waters. Being a heretic does not put one in Hell or the Lake of Fire. If it did then Martin Luther, John Calvin and others will be in Hell because they taught the Truth the Catholic Church rejected.
You first need to define what exactly is a heretic!