I mean no, I've seen a couple of that before. I can only really remember one which is in The Duchess' 50 tea recipes and she feels guilty.
Haven't read the duchess' 50.. yet so this is the first time for me too,I was just thinking about that as well... and I thought it had to do with her finding a character that was already in love with her and continued to be in love with her. Usually they find MLs that were in a relationship but not in love, or not at all or otherwise changed their attitude towards the MC after transmigration. But this time it's someone who loved the previous person, was being put off by them, but then after transmigration thought they got the original character back... so yeah she's feeling guilty.
I’m hoping it’s like a conscious and sub conscious thing. With the weird memory scene it seems like the original is still there, but is just unable to interact with the surface. Maybe as memories of the original keep coming to her they’ll sorta merge into one being.
It's interesting how the girl who got reincarnated worries about not being the same person anymore and tries to stay true to her persona. Like usually, reincarnated characters just try to avoid bad endings or live their life freely, they never actually think about the characters they turned into.