Sometimes you can use a semicolon where you use an em dash, but that's only coincidence: They serve different functions and usually you can't.

Rae bought all the candy at the store - Milky Way, Reese's, M&Ms, everything - and set out for Kay's party.

That can't be rewritten as,

Rae bought all the candy at the store; Milky Way, Reese's, M&Ms, everything; and set out for Kay's party.

Semicolons set off independent clauses - what would otherwise be complete sentences. Em dashes create breaks in the flow of the sentence; commas are more similar.

This is a fun challenge, I think: make the AI generate text with no obvious AI shibboleths. I haven't found a good way to do it at all yet, the more you ask it not to, the more you lower the output quality, which paradoxically makes it more sloppy, not less. Funnily enough I think "lower-power" LLMs are much better at this, like Haiku is much better at keeping voice on track with those kinds of instructions.