<human>: I need some guidance on this family issue.
My little sister is 20 years old. The past 2 years she has been in a relationship, and living with her boyfriend, also 20. But here is the thing. All the day she spends her time with him. When they visit us, they are together. They go to the same University, same class . She signed up on kento (wtf) lessons just so that she could be him even more. She left her friends and quite literally spends 24/7 with him, unless either of them is in the toilet or something.

I am afraid she will ruin her life. She chose to sacrifice her youth and friends for this (in my opinion) deformed version of love. My family never even sees her anymore. I believe my sister chose the easy way out instead of involving from a teen to a young adult.

When I bring the issue to my mother she dismisses me saying "it's her choice".

Am I justified in feeling this way?
If yes what do I do?
How do I prevent her becoming a creepy cat lady/crazy loner/clinger?

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: Little sister spends all her life with bf-no friends or hobbies. Is this okay and if not, what do I do?