I think that would be a hard sell about the first tweet, but otherwise I agree that there should have been an actual investigation into all sides of this situation, not the five minutes it seems they took. I'd say investigate the matter, see if their employee still agreed with the 7 year old tweet (they probably don't), look into the person making the accusation (wow, would that have helped), and then release a statement saying that their employee no longer holds these views, that people need to be allowed to grow, but come up with some sort of lame punishment and / or sensitivity training for optics. Maybe throw some money at a trans charity, preferably one that doesn't help transition children, as that's really the hot button issue here.
Most importantly, never mention who she was following or respond to that element of the story. If they don't agree that they should fire people based on who they follow (which does not equal endorsement), then never even comment on it. Get her to remove anyone remotely divisive from her follows, and then back to business as usual.
Instead they just reminded everyone of how stupid and intolerant Disney looked when they fired James Gunn over his old tweets. Also LOTS of people aren't comfortable with certain aspects of children being given hormone blockers and such, and they basically told all of them "you might think you're protecting kids, but we think you are horrible people, and we don't want your money!" And then you forget about all those people, and just think of the people angry that a company would FIRE someone over a 7 year old tweet.
Combine the two and that's a lot of angry people. That doesn't seem like the best option when it comes to not losing customers.