There are two levels of question/answer here, one being logical/algebraic, the other literary.
Algebraically, all three sentences mean exactly the same thing:
magnitude(terror)=maximum(magnitude(all her previous experiences))
Note that the right hand comparator references the set of all her previous experiences, not just experiences.of terror as suggested by Matt's discussion of 1.
In literary terms, 'on a par with' has a clinical or statistical ring to it, making option 1 seem a rather detached and strange way of describing intense emotion; 2 is close to the spirit of the original.