As Sophia correctly pointed, there is an idiomatic expression like "Ele tem minhocas na cabeça", which is said (informally) when you think someone has absurd ideas. If you say it to a children, they will probably laugh, but they will understand. If you say it in a more formal occasion, people may either laugh or maybe think a little rude. If you say it directly to someone, like in "Você tem minhocas na cabeça", this person will probably get offended, except if she is a very good friend of yours.
So "minhoquenta" is a word that doesn't exist in Portuguese, but it probably derived from that idiomatic expression.
If I were you, I wouldn't bother to memorize "minhoquenta", because I've never seen it written anywhere else. I would prefer to learn "Ela tem minhocas na cabeça" instead.