Your interesting question has two completely different examples.
- You mad?
- She's coming?
The first is a case of Conversational Deletion as described in John Lawler's answer here. This is when we miss out pronouns, auxiliaries and other grammatical words like that in informal speech and writing. It's sometimes called Diary Drop because it often happens in diaries. Many people have studied it in the diaries of famous authors like Virginia Woolf and Winston Churchill.
The second example though is NOT a case of conversational deletion. It is what is sometimes referred to as an Intonation Question. This is when the grammar does not show that the sentence is a question. The structure is the same as it would be for a declarative sentence. We therefore use intonation to show that we are making a question.
Again, we normally only do this in informal speech, and not very often. Learners of English overuse this if their first language only uses intonation and not grammar to mark interrogatives.
It is easy to show that there is no conversational deletion here:
- She (subject), is (auxiliary) coming (lexical verb)?
COME is an intransitive verb so there is no direct object here. All the parts of the sentence are present and correct. Nothing has been deleted. You can also see that the form of the question is exactly the same as the affirmative sentence: She is coming.