Izzy is really Sherry from Mouth to Mouth all grown up.
It makes sense that without no parents to care of her anymore she would stick to what she knew best. The eco-terrorist group was actually CREATED by the security company as a false flag operation to drum up more demand for their services.
This may be lampshaded by the remarks of the CEO who refuses to prevent jams against companies who aren't clients. The final action is actually a test to see if Sarah/Jane is still loyal to the company. She fails.