I think that's also if you are familiar with the No Man's Land story. I have never even heard of that story until like 2015. I was a huge Mainstream Batman fan that had read a few comics and knew some big stories. And I still never heard of that story. And as far as her relationship with Harley. Well for me, that was based on BTAS and Harley was her sidekick.
I think from a lot of mainstreams or casual fans point of view; Ivy is a villain. Not a
"I hate her" villain but one of the greats in Batman's Rogue Gallery. And she tends to stay in that gallery. And she's a great character that I always look for in mainstream adaptations of Batman related stuff.
If some people like her as a Villain, let them. Just like if some people like her as a Anti-Villain or a Anti-Hero, let them. Even if some people like her as a Hero, let them. As long as they are not disrespecting the character or calling her negative names, it's cool.