Some people say that we can talk in the bathroom, basing their evidence on the Hadith of Ayisha (Radiya Allahu Anha) that she used to tell Prophet (Sallallahu Alaihi wa Sallam) to leave water for her when they are performing Ghusl together. Is it true that we can talk when bathing?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

The Hadith you mentioned in your question is reported by Ahmad and al-Nasa'i . Its words are as follows: Narrated Ayisha (Radiya Allahu Anha): "I used to make Ghusl together with the Messenger of Allah from the same receptacle. Each one of us would put his hand at turn in the receptacle until he said to me: leave me some (of the water) and I say: Leave me some" .
This is an evidence that talking in the bathroom is lawful. al-Bukhari even says: 'Mansoor Ibn Ibrahim said, 'There is no harm in reciting in the bathroom or writing a letter without being in the state of Wudu. Hamad said reporting from Ibrahim that the latter said: 'If the person is wearing trousers greet him otherwise do not greet him' .
al-Hafiz says in his famous book al-Fath: 'If reciting (the Qur'an) is lawful in the bathroom then saying any other thing is lawful in the bathroom. Some scholars disliked reciting in the bathroom and they differentiate between reciting in a pure place where there is no exposure of the Awrah and reciting in other states.
It should be stated here that the bathrooms were separated from toilets in those days. So, if a toilet is in the bathroom one should not recite the Qur'an or remember Allah in that place.
Allah knows best.