The correct option to fill in the blank is dilemma.

The word "dilemma" refers to a situation in which there are two or more options, but each option has its own drawbacks. It is the most appropriate word to use in this context, as it conveys the meaning of Prerna being in a difficult situation where she is not sure which option to choose.

The other options are not as appropriate.

• Pain refers to a physical or emotional suffering. This is not the right word to use, as it does not make sense to say that Prerna is in pain about whether to go for the party or not.
• Depression refers to a mental health condition characterized by feelings of sadness, hopelessness, and worthlessness. This is not the right word to use, as it does not make sense to say that Prerna is depressed about whether to go for the party or not.
• Distress refers to a state of great suffering or anxiety. This is not the right word to use, as it does not make sense to say that Prerna is in distress about whether to go for the party or not.