Thank you so much for the detailed response. Should I not even do water changes? Just leave the tank for a couple of days?The Tetra Whisper filter has 2 inserts. The plastic insert is supposed to be the bio filter. What she changed is the filter pad with carbon. It shouldn't be a problem but there is a significant amount on the filter pad. There's really no need for carbon so you can cut the filter pad and dump the carbon and just reuse the filter pad after rinsing it in tank water (in a bucket).
Tetra says to replace monthly so they can take your money.
You don't need Prime if you already have tap water conditioner. Everyone here likes Prime but it's not going to do much for you now. I would recommend it as a water conditioner as it can also detox ammonia, nitrites, nitrates and heavy metals but you can get it after you use up the API conditioner.
BB grows on all surfaces that tank water touches. Filter, gravel, plants, decorations, glass, etc. You are most likely experiencing a mini-cycle and should be fine after a few days. Don't scrub the tank. A spotless tank is an unhealthy tank.