<human>: I will try and keep this as succinct as possible

My girlfriend has been in a long term relationship since she was 17. We started dating 2-3 months after she and her ex had broken up. And we have been together for 3+ years now.  We went to the same college and spent plenty of time together, but were no means attached at the hip

Last night she told me that she had been thinking about how for the past 4 years she's always been in a relationship. Because of this she feels she has been unable to grow and develop into 'herself' and thus may or may not want to break up so she can find herself

I am at a loss. I have no idea what she means by this and asking her to explain did not help. I want to understand and be able to help with this.

She is the best thing to ever happen to me and I would do anything to make sure she is happy. I also don't want to lose her, and I'm fucking terrified that if we breakup it will be the end.

Thanks so much for taking the time to read. If I'm being and idiot just tell me

Can you summarize the given text in a few sentences?
<bot>: Girlfriend feels being in long term relationship(s) has not let her become herself, how do I understand/help?