Select the idiom that means the same as the underlined segment in the given sentence.
She forgot to apply for her internship abroad due to the ongoing marriage preparations she had to help with and now that opportunity is lost.

The idiom that means losing an opportunity due to being too slow or failing to act in time is Missing the boat.
Meaning of other idioms:

Burning the midnight oil: To work or study late into the night.

Beat about the bush: To discuss a matter without coming to the point.

Treading on thin ice: To be in a risky or dangerous situation.