I do think your worries are not completely unfounded (don’t panic, I’ll get to this) but the pediatrician is the last person who can help you with that.
Toddlers as verbal as yours are probably like 1 in 10.000 or something. You will know the statistics better than I, it’s your job, and you’re right that it is almost impossible to find at least one kid who will “match” your daughter. I still recall my oldest’s utter frustration when he was a super verbal toddler, and my huge relief when *something* worked, even for a short time.
The good news is, it is not really necessary at this age, because she is probably still just as happy or even happier to have your company and attention, or a loving grandparent’s attention. As you no doubt also know, kids that age engage in parallel play still. While it may seem to you as if she were ready for full cooperative play if she had a fully verbal peer, that part of he development probably isn’t quite there yet. Your mileage may vary, my oldest actually turned out to be somewhat delayed in play development, my middle daughter was early and could engage in some cooperative play with another super verbal toddler girl at around 2.5 or so. But while for short moments it was like having two 5 year olds in the house for a play date, they needed intense supervision and help every so often when it smacked you in the face that no, they were two, and utterly incapable of dealing with more mature give and take.
So, try to pick activities. Do stuff with the other highly verbal 3yo where they can do lots of running around. Find a quiet little girl who enjoys stringing beads, too, or will play happily in the mud alongside your little girl while she plants flowers or something. Sometimes kids a bit older or even a bit younger work better than same age peers because kids instinctively adapt to different developmental levels in mixed age groups. Sibling groups, if you have them among your friends, are great for very asynchronous little kids, because there are so many developmental levels around at once, and kids with a lot of siblings tend to be more tolerant.
Start researching preschools and elementary schools now. Try to find schools with mixed age groups, with a contingent of highly educated (not necessarily wealthy) parents who are more likely to have very verbal children as well. Montessori doesn’t work for every gifted kid, but your daughters temperament sounds like it might be a good fit, if done right. Most importantly (and that one can be a problem, specifically, with Montessori, but also schools who profess to cater to the “gifted” but who really just look for bright kids rom high SES familiies) look for flexible teachers, without preconceived notions, ready to accept that they may be looking at a kid the likes of which in verbal and probably overall cognitive development they haven’t seen before and may not soon again. And who also understand that she’s still just a very little kid who may be all over place developmentally otherwise.
