Yes, you can always change your mind.
The trick to the spray is you're not actually pouring the water on them and it's quite quick with a little spray bottle. If she is afraid of this then it would definitely be a quick fix. In My Opinion, it would only damage her trust in you if there was no way for her to avoid the water, leading to helplessness. I think she would learn quite fast to sit in front of people with a treat if she new the consequence. Also, you can spray her and hide the bottle behind your back. She wouldn't even know where it came from, haha.
See, the thing is, you need to make it quite clear to the dog what reward they get for the desired behaviour and what punishment they get for the undesired behaviour. The greater the contrast, the faster they learn.
I hope the time outs work for you, but from my experience, it can take dogs a little while to join the dots (if they do at all) and I'm pretty sure that in the wild the older dogs don't send the pups for a time out when they jump on the other dogs, they give them a quick nip and tell them that's enough. The dogs get it and move on, no grudges held.
Good Luck with your training I can't wait for your update in the future.