It will depend a good deal on the operator. There aren't government regulations in this part of the world saying that this or that dive is accessible only to AOW divers....
For example, in the case of Phuket (with which I'm intimately familiar, unsurprisingly!) you can join any trip as an OW diver. Some operators may limit depth, however, because of accident and liability worries. The situation is similar in other areas. I generally counsel AOW for our liveaboard trips here in the Andaman Sea because there are night dives, deep dives, and dives where there are other circumstances, such as currents, that are less common on the "easier" dives that most OW divers do. I would wager that your wife would receive as good a quality of AOW training from me here on Phuket as she would at home, and in much more enjoyable conditions. I often provide AOW courses on board liveaboard boats as well, so there is convenience as well as the fact that when I do those sorts of courses, my student divers are with me for three times the number of dives than in a standard AOW course.
For example, in the case of Phuket (with which I'm intimately familiar, unsurprisingly!) you can join any trip as an OW diver. Some operators may limit depth, however, because of accident and liability worries. The situation is similar in other areas. I generally counsel AOW for our liveaboard trips here in the Andaman Sea because there are night dives, deep dives, and dives where there are other circumstances, such as currents, that are less common on the "easier" dives that most OW divers do. I would wager that your wife would receive as good a quality of AOW training from me here on Phuket as she would at home, and in much more enjoyable conditions. I often provide AOW courses on board liveaboard boats as well, so there is convenience as well as the fact that when I do those sorts of courses, my student divers are with me for three times the number of dives than in a standard AOW course.