Emily's Cat
Rarely prone to hissy-fits
So, she's a TERF, not a TIRF. Or at least shes a TEF. Although after reading d4m10n's link I'd say she is radical, just not extremist.
I'm also probably more of a TERF than a TIRF.
Rowling isn't a radical feminist though. Radical Feminism is a specific branch of feminism with a specific set of ideas. A surface viewing of those ideas would probably apply to nearly all feminists. But a deeper reading reveals some differences that don't transfer over. For example, Radical Feminism holds that males as a class form an intentional structure of oppression, and that males are entrenched in that power and take steps to maintain their intentional dominance over females.
That's not a view I hold, and I don't believe it's a view that Rowling holds either. Rather, there is a tendency for males to just not think about females as being separate from males. It's not intentional, it's lack of thought in most cases.
For example, most vehicles are build to male physical specifications. The seats, the button locations, the seat belt positions are all based around the average male build. That's not how females are built. A lot of seat belts hit females in the wrong place - they don't cross our chest from outer shoulder, across chest, to waist. In a lot of cases, they actually start traversing our bodies at the neck, and instead of the center of the crossing being just above the diaphragm, it ends up being just below our collarbone. This puts females at greater risk of injury in a collision than males.
A Radical Feminist would hold that this is intentional, because males build for males with the intention of excluding females. To the extent that this isn't the impetus for ALL males, those other males are silent partners in the continuation of the oppression of females, including through increased risk of injury.
A Classical Feminist, however, would hold that this is not intentional. It's a result of males being in positions of power for so long, that even when they are nominally supportive of equal treatment... they don't think about it. It's the "Invisible Knapsack" of male privilege, not intentional oppression.
A lot of Radical Feminists support Female Isolationism, Political Lesbianism, and a lot of fairly anti-male separatist ideas. Not all of them, but that's the only faction of feminism where you're likely to find those ideas surfaced.