In the aftermath of Order 66, there is a small group of remaining Jedi and senators who know the truth about who Luke and Leia are and why they must be protected. Yoda leaves in exile to Dagobah, but Obi-Wan and Bail make the decision as to where to place the twins. Obi-Wan takes Luke to Tatooine to live with his family, but Obi-Wan stays there to keep himself hidden and also watch over Luke as he grows up. Bail, on the other hand, seems to be on his own on Alderaan - this answer (Did Bail Organa tell his wife about Leia's parentage?) seems to imply that Bail didn't even tell his wife the truth about Leia's parentage, since he said in a recording from Bloodline that he wanted to tell Leia this himself.
There was the possibility that Leia would be Force-sensitive, the same as Luke, and that she would be in danger because of who she was. While it is perfectly plausible that Bail's status would give Leia sufficient protection, which is why Obi-Wan left to watch over Luke, it made me wonder - was there anyone else watching over Leia?
It makes sense if there wasn't anyone else, and because the number of people left who knew about Luke and Leia was few, but I am wondering if there was someone else who was watching over Leia as she grew up on Alderaan.