I have noticed this a number of times in Coliseum (as that's the only place I use Spider), and I have mostly noticed it when Bard is the victim. Basically what happens is:
- Spider ascends
- Spider descends onto Bard, cocooning him
- Spider successfully puts Bard in a cocoon
- Plant activates white, defends Bard
- Bard is now out of cocoon
This part I am less sure about since sometimes the game is moving pretty fast, but I am fairly certain that after Bard breaks out, Spider cannot reactivate her white, even with full energy, until Bard dies.