Perhaps Guinan knew what Q inadvertently provided and that Picard realized at the end, that Star Fleet really did need a 'kick in our complacency' if they were to adapt and handle the challenges that were to come as they continued to reach farther into deep space. Therefore she had to allow Picard & Co to figure out just how bad bad was on their own, so that they would truly understand the threat that now would exist and would be able to relay the urgency to Star Fleet.
Agreed. Although, I think it was Q's intention to teach Picard and the Enterprise a lesson. A very important lesson too. Guinan understood this.