So, I choose one of my pets to be blessed but I accidentally clicked on the wrong one. ('m in the gem questing page) How do I end the quest to go back and choose another pet?

It's not possible to end the quest unfortunately. :( You'll need to finish it and start again.

Do you know if the quest would reset if I waited till tomorrow?

The quest won't reset, ever. You won't be able to make another pet galactic until you change the one you already selected. :/

Oh, okay. I just wasn't sure this is the first time I caught it. But, it's cool. Thank you. C:

Just for future reference, the Hydrus quests work the same way, so if you ever want to do one make sure you're extra careful about which pet you click. :)

Thank you. I'm going to have to decide how much I want this pet galactic now. xD;