My girlfriend f22 ended things randomly after five years with me 25m

I 25m and my girlfriend 22f have never had more than 4 arguments over our entire 5 year relationship. We have lived together the entire time we’ve been together and haven’t spent more than 3 days away from each other. Recently she stayed at her sisters house for 10 days to take care of her animals while she was away on vacation. Seemed a bit odd to me considering she didn’t inform me that she wouldn’t be coming home during that time and it isn’t like her sister lives super far. Her house is literally 5 minutes away from my girlfriends work so whenever I heard that she was going to be taking care of the animals I assumed she’d stop in before work on her lunch break and on her way home but this was not the case. She packed up her stuff nothing unusual just mainly clothes and makeup. And out she went and I’m not going to lie I was pretty salty about the situation but I didn’t say anything because I figured we would make plans to see each other. Fast forward during the week she was away not one time did she try to invite me over, call me, ask about our own animals or have any substantive conversation. I know I’m also wrong for not trying to make plans but I will say it was mainly because I was still hanging on to why she told me the night before she’d be gone for the next 10 days. Anyway one full week after she originally left to go stay at her sisters house she sends me a message expressing that we should break up. And it was not a long thought out message, probably 6 to 7 sentences max and there was only one vague reason that she said was the reason for it. It was that she felt like we had just become “roommates”. Now I didn’t disagree with her about that because we had been in a rhythm in life where things were kinda just slowing down. I told her that I agree with how she feels and that it’s not because the love isn’t there we just haven’t done a good job at putting enough effort into us. I also said that it is something that all relationships go through especially whenever both parties work full time and just wanna get home and relax sometimes. Nevertheless we had a series of conversations that ended off in a better stop than they began and we would start the next day and her vibe would do a complete 180 of how we ended the conversation just the night before. My issue with all this is that she never mentioned how she was feeling before all this started at all. Everyone in our life was dumbfounded when they heard about what is going on. My other issue is that she is completely unwilling to work to fix things one bit, I have been understanding and and reasonable in our talks and she just doesn’t have much to say other than she doesn’t feel the love and that its a gut feeling that even if we do work through things that it’ll just end up back at this point. This whole thing is very out of character for her not just with the way that she’s treated me during it but also how she is closing off other people in her life about talking about it. She is also just carrying on with her life as if nothing is going on at all. I just never saw this coming and I don’t understand why I am not getting solid reasons for this one sided decision and I’m not sure how I’m supposed to handle any of this because like I mentioned before we never fight and this is not normal behavior from her. I keep convincing myself that she’s having some type of mental episode because there are other factors in her life that I know have been really hard for her and I feel like I am the one that is receiving any type of punishment. I’m just really lost right now and wish that I could know what happened the 10 days she was away. There’s also more details I can provide if anyone needs them but yea has anyone had a similar experience or any advice for me?