I don't have an editor.
My only attempt at a stand alone resulting in the first dozen reviews all calling for a sequel or trilogy. I did the trilogy, but started with only 1.5 books worth of story ideas.
If your editor is saying make it a trilogy, it's most likely the ending leaves a lot of questions unanswered, and readers will pick up on this and down-star you for it.
If you don't want to take your editor's word for it, have a few beta readers read it as well, and see what they say without asking the question at all.
Editors are not always right, but if several other people all say the same thing, you can assume it is right.
The other thing is go back to the editor and ask why it should be a trilogy. And make sure you get hard answers, not waffled ones. There should be actual reason for continuing the story on.
If nothing else, you might find you can edit the existing story to fix anything left open, and thus not need a sequel.