Context: I'm a grad student and working part-time.
The relationship situation: We've been together for pretty much exactly 2.5 years now, and we've been cohabiting for a while now. She'd gradually spend more time at my place until she basically lived with me.
The living situation: For the past 2 years I have had a shared apartment with a friendof mine. We have a shared kitchen and bathroom, and we each have a 240 sqft (22 sqm) room. Our lease is nearing its end, but we do have the option of renewing it, but we do have to decide very very soon. I also have another option: my mom has a big 1400 sqft (132 sqm) apartment that me and my gf could move into it. For the past 3 months my gf and I have been living there as a sort of "trial phase". Moving there permanently would save me a ton of money of course, the only downside is that my mother would also occasionally live with us (for about 10% of the year) and it's just not a great dynamic with her and my gf tbh.
Now onto the far bigger issue: I just don't feel ready. When I first entered college and moved out from my parents I was hopeful, I was looking forward towards "reinventing myself" and imagined just how great life would be. I pictured it being something like the college frat lifestyle you see in movies. But then Covid-19 hit and my social life was effectively 0 for almost two years, and then I got to know my girlfriend and at first it was quite complicated… She was (and still is) depressed, and would require constant attention. It was so bad that I became socially isolated from my friends yet again for another two years, to the point that I'd only be meeting up with a friend once every couple of months. It feels like I just skipped 4 years of development that I'm still 20 mentally but my body and responsibilities are that of a 24 year old.
I still want to live the college dorm lifestyle, but the window is closing. and I absolutely can do that if I just renew the lease. I get on really really well my flatmate, we have a shared friend circle and we just vibe. We could most likely be best friends if I only spent more time hanging out with him. I still have the opportunity to experience the life I so badly wanted if I stay in the shared apartment. If I don't, well that's it, I will never have this opportunity again.
I tried talking about it to my girlfriend but she is vehemently opposed to the idea. If I were to move back into the shared apartment I'd spend less time with her because it gets quite claustrophobic if you only have one room available for the two of us, and I sometimes need my space and alone time. She feels like it's a step back from where we are at currently. because up until now she's basically been living at my place 24/7. She says it feels like I'm kicking her out of the apartment, that it seems like I'm getting cold feet and trying to avoid commitment.
And I suppose she is partially right about that… Right now my life outside of work and study time looks like this: 80% girlfriend time, 20% alone time. And right now I'd prefer it to be more like: 33% gf time, 33% time with friends, 33% alone time. She says it feels like I want to downgrade from workimg towards marriage eventually to just dating casually, and that she can't do this after us having been together for several years. And my POV is that I never got to really life my own life the past couple of years (because of me solely focusing on catering to her) and that I'd be unfair towards me to expect me to just lose out on that phase of life entirely.
I only have a few days to decide on whether to renew the lease and I have absolutely no idea what to do.
Tl;dr: girlfriend wants us to move in together but I feel like I'm not ready yet because I missed out on a lot. How do I discuss this with her?