I used to shave the ears for shows. Some horses don't give a flip, some HATE it but learn to tolerate it. Takes a while for the ones who hate it, and I can't say I blame them. Hold the clippers (not the blades) up against your head behind your ears and see what its like!
If you don't have to do it, I'd not shave the ears.Maybe trim up any goony hairs that hang out in tufts to make it look tidy, but I usually do that with scissors cause it's too much trouble to plug in the clippers for that .
However, getting your horse used to the vibration, even if you never shave them, is a good lesson in trust and respect if you do it right, so use this as learnng opportunity! The muzzle is a good place to start since she was okay with that. Basically, work your way up (just rubbing the clippers, not the blades) , advance and retreat. Advance to where she starts to get concerned, the retreat to a previously okay place. Do for just a couple of "advances" every day, even if you only progress 2 inches higher than the day before. Just do it casually and for a couple of minutes.That keeps it from becoming a big deal.
You may have to start at the muzzle every day, but eventually you will get to the ears. Don't make it a 30 minute session. the first time by the ears, just go gently in a quick move, and retreat to the last "okay" place and quit, The next day you can do for a little longer, etc.