Of course nobody will ever know, but Apollonia was very young, immature and submissive. (I believe 16 when they got married.) I cannot conceive she would have exerted much "influence" on Michael other than essentially support whatever he wanted to do.

Kay on the other hand was a college graduate and had a teaching career of her own, and as we later learn, is independent enough to stand up to Michael (sometimes). I cannot imagine Apollonia doing any of that.

She was, however, simply outstanding , in her one big scene...