This is true, but it's not enough. In particular, there are two trends that one would need to show aren't the case for JKR in order to get a genuine transpobicity-free label. (1) The enemy of the enemy is my friend effect. People who are actually anti-trans see JKR as the enemy of their enemy. Has she resolutely avoided doing the same in reverse and thus avoided picking up transphobic outlooks where previously she had none? (2) Reciprocal animosity is the easiest thing in the world to fall into. And it's sensible and justified if you target exactly the people who are treating you with animosity. But it's tough to maintain really precise category boundaries while doing this when you keep getting attacked by some new trans person or trans advocate.

(Tip for X-actvists who want an Xist enemy to rally against: pick anyone and treat them like your worst enemy. Chances are very good that they'll hate you, and because you're an X-activist, they'll start hating X, too. Presto! Now you have someone to rally against!)

So I think the kind of evidence you show here isn't particularly conclusive. It indicates that she's not the most viciously transphobic person possible. But you'd need a closer analysis of the kinds of things she does say to rule out a milder transphobicity.