One day she decided to get away from everyone, because there came a point where she was so overwhelmed and submerged in a hole without seeing a way out; that she felt that she couldn't take it anymore, she was so alone and surrounded by people that it was best to go into temporary isolation, not forever. Whether it's to scream loudly, cry or just be in total silence, sleep a lot or think for long hours, basically getting away from people is sometimes necessary, not as something bad, but to take a break.
Definitely, it can be somewhat surprising and it is even difficult to understand why someone makes the decision to isolate themselves, especially since it is not precisely due to a case of illness. So it's about something social, it's a point where someone wants to get away from people and usually doesn't want to give many explanations, in fact none at all; he just wants to do it and leave without saying anything.
I believe that this human need should not be a strange attitude, on the contrary, it deserves more understanding; because yes, sometimes, you can also get tired of people and you beg for a break from them. It is valid that there is some concern for those around you or those who miss you because they stop seeing you, in that case you could tell them that you will be fine, but that you need a moment alone. It can be a long or short time, as long as it's necessary, it's okay to walk away sometimes.