Looks like she is clairvoyant enough to guess the contents of the box. A joke becomes a practical. The good point is that they were warned much before it timed out and an explosion took place. Jen is wise enough to guess her ex husbands cruel intent to bomb them, they being "mafiosi" previously. Habits do not change that easily.
Drama-
No doubt it must have been pretty shocking to the new husband. There are no hysterics but surely there must have been shocks with the stunning revelation of the gift.

Writing style-
Short crisp sentences that show without telling.
"She considered her options, and then cut the red wire. The ticking stopped."
Her actions also show her experience that made her smart enough to deal with a challenging present.

The snide remark at the end is dryly humorous.

Write on!