Fouls should obviously be graded on some sort of severity system. In the first place, they already are to an extent: fouls either get nothing, or a yellow card, or a straight red. But occasionally even a straight red isn't enough to fit the "crime", and a longer suspension is necessary.
In this case, for example, it obviously makes a difference that Lauren James didn't stamp with any great force, and didn't target the head or something -- either of which would have surely justified a suspension measured not in matches but in months, or at any rate something far more than just a one- to three-match suspension. Also, it evidently *is* relevant that the victim has forgiven her and moved on, if nothing else because it reinforces the point that there was no serious harm done.
This was stupid, reckless, and deserves to be condemned; and a punishment to the effect of keeping her out of the remainder of the tournament is reasonable. But it wasn't especially dangerous, or violent, or career-ending for the "stampee".