‘I went out with Jo on Sunday. She looked awful.' ´She` clearly refers to Jo, there is no need to repeat her name.
In the classroom
Asking learners to identify what or who the pronouns in a text refer to is one way to raise awareness. They can then practise this by using pronouns to replace words themselves. Comparing texts with well managed referencing to ones with poorly managed referencing can help students develop an idea of effective referencing even at low levels.