spoilers for book 12, 13 and the beginning of 14:)

If Bumblebee was only stung by Wasp once, how would that confirm that Bumblebee can't be controlled? It would depend on how much of the other mind was injected into her. For this let's just say an amount that was equivalent to being injected twice was in her. That would probably let the other mind and/or Wasp see through her eyes. If Wasp were able to control Bumblebee and see through her eyes, Wasp would be the first one to find out if Bumblebee has a weapon, like venom in her teeth, a stinger in her wrist, a stinger in her tail, etc.

If Wasp/the other mind found out that important info first, that would not be very good for the dragons that are now at Pyrrhia. Let's say that Wasp could control Bumblebee and saw through her eyes what was happening on Pyrrhia. That would be chaotic. Wasp would be able to control her as well, which would make it even harder to defeat the other mind.

Now, let's say that Bumblebee was injected with barely any of the other mind's plant thing. Then they would most likely be safe. But there would probably be drawbacks. An example would be; Wasp can see through Bumblebee's eyes but not control her, or if Bumblebee was injected with more of the other mind's plant she wouldn't have her eyes be white. 

thats kind of it but yeah