I think some of the posters in this thread are showing a fundamental flaw in their belief of how Hashem runs this world. (Not that there is any flaw in their Emunah, rather there is a logical flaw in how they apply it.) Some posters here seem to think that if a Sefer has a Segulah, it is an absolute guarantee that this will happen. This is, obviously, not true. Whenever you state an absolute, you will be wrong. (Slightly relevant anecdote: I know someone who went off the Derech because he had a friend who earned a fortune on Tishah B’av and the Gemara says that someone who does business on T”B won’t ever see a Siman Bracha with that money.)
The Gemara itself, however, acknowledges this. The Gemara (maybe Kiddushin 39b?) mentions that one of the reasons that Acher stopped believing was because he saw a kid who was doing a Mitzvah die while doing it. The Gemara then asks how that could have happened in the first place. One Tanna (Amora?) gives the answer that in a dangerous situation, a Shliach Mitzvah can be hurt. The Gemara then rejects that answer and doesn’t provide one. We have a K’lal that a Shliach Mitzvah is never hurt.
How, then, can this assurance go against reality? The point is that HKBH runs this world and has to decide what happens on an infinite scale. While it may be that, short-term, a Shliach Mitzvah is protected from harm, that’s only when all else is equal. Sometimes HKBH just has overriding concerns to take into account.
So too here. It’s silly to say that stepping on someone’s foot will determine her every decision for the rest of her life. That’s just obviously not true. What it means is that she will have much more of an inclination to be the more passive one in the relationship if someone would do this.