Learn English – Has vs. might not have been

Neither sentence is grammatical English or something that a native would typically say, so it is pointless to argue over what they might mean. I don't see a reason to correct them differently.

“*This would not have been happened” is a passive construction. But happen is not a transitive verb, so it cannot be used in the passive voice. It is likely that the author of this sentence intended to write “This would not have happened”, i.e. the event mentioned previously would not have taken place.

In addition to the previous defect, “*this would have not been happened” is incorrect because the negation cannot be placed where it is. The negation word not is normally placed after the first auxiliary: “this would not have …”.

Furthermore, the second part of the sentence is in the wrong tense. “This would have happened” is a past conditional. The part of the sentence introduced by if is a past hypothetical. It needs to be in the past tense because the time of the action is in the past; in addition, the hypothetical aspect is expressed by a past tense, which means the verb needs to be in the pluperfect tense: “if you had not been there at that time”.

A correct sentence resembling these two incorrect sentences is

This would not have happened if you had not been there at that time.

I can't think of a correct sentence with a different meaning that could be what the author was trying to express.

It is probably true that the mother is still pushing the daughter to do her homework.

However, the mother's pushing the daughter now does not provide a reason for the daughter's having done well on a past exam. That can only be attributed to pushing in the past. Consequently, the perfect is in order here.

Note that this is an experiential perfect, not a resultative perfect—it characterizes the pushing as an element in the mother and daughter's current shared experience. The resultative burden is carried by the preposition because, and in a formal argument this would call for a simple past or past perfect (and in fact, most US speakers would probably employ a simple past here: "You got an A because I always pushed you."). But that sort of precision is unnecessary in colloquial contexts; in the context of a present or perfect in the main clause the present perfect maintains temporal harmony between the two clauses—"You've {got / gotten} an A because I've always pushed you."