Though it can also be used as a sarcastic retort.
The sarcastic retort usage of the term, would be something like, when someone was jealous of someone. The person might say: "Hey i got a date with that fella! and you would reply, "I'm made up for ya!" (when really you were no such thing)
1. Something fabricated or a fictional topic, usually thought-up on the spur-of-the-moment.
2. Something not yet widely accepted/ verified as true.
3. Vt. (Primarily feminine); To be ready to go socialize.
"I'm almost madeup for tonight's speed-dating buffet".