Female friendships important to Mountain Gorillas

[Catherine]

Years of study of Mountain Gorillas are teaching us things about their social interactions. Female gorillas form bonds and appear to maintain them even when they are separated for some time.

https://www.bbc.com/news/articles/c80d7l94yvro

This does make sense. Think of how humans interact. Female bonds are important. 
They would be even more important to a gorilla troop. Primates are social beings. Our interpersonal connections are necessary for our social structures to survive. 
The gorillas need their troops to function as a group. They don't live as individuals. It is certainly safer for them to live as a social group.