If she wasn't, she could have said:

"Theodore, you mean to tell me I came all the way here from Bell Port, for you to tell me you're not going to Fall Brook? Give me back that beanie!"

And that short pants suit I bought you!

Yes! LOL!!

I thought she lived in "that poor house in Riverside?" Anyway in the short pants episode Aunt Martha flies to Mayfield and in Beaver's Prep School. When they take the train to visit her it's much closer. I'm sure she had a nice visit with June and used the guest bedroom.

This reminded me of the one when Wally wanted to go to Bellport Military Academy and then didn't want to.

The flying thing is interesting, since she and the lady who played Mrs. Elkins on Dennis TM, visited, when the boys wanted to go to the carnival. They were driving somewhere (and were misdirected, according to Mrs. Elkins), so she had to live within reasonable driving distance.

Also, how did Beaver get to Aunt Martha's when he visited her, on the episode where he was turned into a rock?

That's right there were many times that Aunt Martha visited or the boy(s) visited her. She either had to take a plane or just drive to Mayfield. The boys took a train or Ward drove Beaver to her house. Another inconsistency like Gilbert Gates, Harrison, Bates.