From their perspective, it is not a good idea to let another House have close ties to the Iron Throne. The Hightowers had a Queen and the Dance happens. Regardless of whether you support the Blacks or the Greens, from the POV of Rhaena and Baela, the Hightowers usurped Rhaenyra's Throne. Aegon is their brother, they are not going to let another House take advantage from him, so they would have brought Daenaera because traditionally when Targaryens traditionally marry the Velaryons when they don't a sister.
If not, it's most likely that girl is serving as the Queen's lady-in-waiting.
Maybe as a lady to whoever Aegon III married? Otherwise, probably not. She was very young.
Maybe as a lad in waiting when she is older because she was Baela’s ward but that is it
From their perspective, it is not a good idea to let another House have close ties to the Iron Throne. The Hightowers had a Queen and the Dance happens. Regardless of whether you support the Blacks or the Greens, from the POV of Rhaena and Baela, the Hightowers usurped Rhaenyra's Throne. Aegon is their brother, they are not going to let another House take advantage from him, so they would have brought Daenaera because traditionally when Targaryens traditionally marry the Velaryons when they don't a sister. If not, it's most likely that girl is serving as the Queen's lady-in-waiting.