Part of the answer to your questions lies in the fact that Cleopatra's Egypt was never a province of Rome. Egypt was only annexed following her defeat in the Final War of the Roman Republic and it was organised into a province during the reign of Augustus, Rome's first emperor.

Prior to this, Egypt had long been an ally of Rome which leaned on its military support while at the same time extending resources like grain, money, ships and auxiliaries to its growing friend in the west. It is true that various Roman politicians intervened in Egypt's internal politics but this was at the behest of an Egyptian monarch, or claimant, and this sort of outside arbitration was not unprecedented in the ancient world.

You might enjoy these posts of mine which can shed some light on the matter:

What was the relation like between Ptolemaic Egypt and the Republic of Rome?

What would you say were some reasons the Ptolemaic dynasty ended?

What happened to the Ptolemaic Egyptian bureaucracy after the Romans took over?

Were the trappings of the office of pharoah maintained in any way in Roman Egypt?