Rachel, I going to be completely honest here (and speaking just from my personal experience). Feel free to disagree.
First of all, if you only
look into dressage I don't think eventer would be the best choice (unless you are very lucky). IF you look into eventing and jumping, then yes, I'd go with eventer. Otherwise I'd look for true dressage trainer. Many eventing trainers in my area in fact take lessons with dressage trainers, so there is a reason for that I'd think. Lol!
Another thing I noticed (I went through number of different instructors different levels), I worked the best with very seasoned trainer who knows/sees exactly what I'm doing wrong and goes after my position and cue every min (or every other min
). All younger instructors I worked with mostly just gave instructions, that's it, and I was not improving. I'm NOT saying it's always a case, I'm saying it was my personal experience. Now, it's not for everyone, because 1) majority of time it's not sugar-coating, 2) not everyone likes to be corrected constantly, 3) those seasoned instructors make you work very hard during a lesson and not everyone likes/can handle it.
And the most important: the great rider is not necessarily a good trainer. Very often it's former but not latter. The instructor you posted is no doubt a good rider, but she sounds green as a trainer. Again, it's all a matter of taste.
If you like her - give it a try!