Reactivating Rhonda requires a Science skill of 60. If the Courier reactivates Rhonda and chooses to lead it to Tabitha, they will complete the quest "Crazy, Crazy, Crazy", as Rhonda and Tabitha wander off together.
Effects of player's actions
If the Courier killed Tabitha beforehand, Rhonda will ask what happened to Tabitha. When informing her about Tabitha's death she will become hostile towards the Courier.
If you wish to peacefully resolve the situation with Tabitha, ensure that you do not let three days of in-game time pass between the moment when you first encounter Rhonda and the moment when you decide to repair her. Rhonda will disappear from your game if you leave her room and decide to come back in three days, due to her being set to never respawn.
If you reactivate Rhonda and spend too long in the supply room, Tabitha will appear and both of them will attack you.
After you reunite Rhonda and Tabitha, if you have the Robotics Expert perk, you can sneak up to Rhonda and deactivate her. Tabitha will then simply stand behind Rhonda and will still talk as if following her. Tabitha will not become hostile and there seems to be no way to reactivate Rhonda.