The people in the crowd understand Aunt Martha should have been set free
Yes, it seems to be an alternative, in some situations acceptable, but eccentric and not neutral spelling of this word. It accents the fact that "ea" here are two separate vowels rather than a diphthong: that is the function of the trema (the two dots).
In practice it's not used much, because it's not really necessary: it does not distinguish it from any other word, and trema is not easy to find on English keyboards: so there is no need.
Assuming that this is referring to the same passage that was posted before with this question, the editorial writer's main point is that "The mayor and city council have made a serious mistake in selecting a site for a new community theater" since he expresses this more than once.
Are you looking at diagrams on you work sheet ?
