Answer: to watch
Explanation: The gerund is defined as a form that is derived from a verb but that functions as a noun, in English ending in -ing. The infinitive is defined as the basic form of a verb, without an inflection binding it to a particular subject or tense. So, choose the -ing word (watching) and make it the infinitive (to watch).
If maybe she tested out an airplane or something like that and it broke. Or if she said "what could go wrong?" or if someone mentioned something about her hurting herself or breaking her leg.
