This is my understanding of the rules for this situation.
The first thing to keep in mind is that downwind finishes are handled exactly the same way as downwind gate marks. The rules make no distinctions between the two so anything that would apply at the gate also applies at the finish.
Prior to postion A, it's assumed from your description that orange was clear ahead. Blue created an overlap to leeward from clear astern. Once the overlap is established, orange is required to keep clear of blue. Since blue established the overlap from clear astern, blue can not sail above her proper course (i.e., blue can not aggressively luff orange), however this does not relieve orange of her responsibility to keep clear of blue. As long as they remain outside of the three boat circle, blue can sail as far from the mark as she wants before jibing.
Orange should have either footed down early to prevent blue from going below her or heated up to maintain separation and allow room to jibe in front of blue when there was still space. Once the overlap is established, orange's only real option is to jibe after blue and follow her to the finish or slow down and jibe behind blue.
Position B is unclear whether this occurrs inside or outside of the three boat circle. If outside the circle, blue is entirely in control before the jibe. After the jibe, since there is no overlap, neither boat is inside the other, blue is clear ahead, and orange must keep clear.
If the boats are overlapped when they reach the circle, the inside boat is granted mark room and the outside boat needs to keep clear even if the overlap is later broken. In this case, orange is the inside boat and blue would need to bear off and/or jibe once she reaches the circle to give orange mark room. I agree that the wording/definitions of the rules are little unclear but since the mark must be rounded to starboard and orange is on blue's starboard side, orange is the inside boat.
The reality is, once blue established the overlap to leeward, it was pretty much game over for orange.