I have loads of memories up until from I was just turned 4. I can describe the house I lived in in a lot of detail, the playgroup I attended a handful of times age 3, going to see someone, who was dying when I was 2 as they gave me something. My mother was incredulous when as an adult I just matter of described the hospital visit and accurately describes the present she gave me.
Other people have fewer memories, some will have more. Just because people don’t necessarily actively remember something, it doesn’t mean they cannot be affected positively or negatively by an event. Babies are little sponges and a product of their environment.
You were doing your best op and I think this has really upset you because of your feelings of guilt from this time. Children don’t come with a manual. However, I don’t think it is useful to dismiss this as your dd is privileged so file this in the bin marked brat. It could be in part that she’s made this up in her head because she’s sensed or heard your guilt but I would treat it as real. Perhaps she wants to fit in with her friends and this is a way of doing it. She only knows her experience and fighting against this, invalidating her feelings right now isn’t going to make either of you happy.
My dd is also massively privileged and is acting rather spoiled at the moment. However at 13, she only knows what she knows and cannot imagine what it is like for those, who have difficult lives, fewer opportunities or inattentive parents. At times I get cross with her complaining and yet know if I koko, it’s just another stage, which will pass.
If you make this about how much more privileged she is than her friends, you’re othering her, making her appear ungrateful. It won’t go away. She’ll just pull away. All you can do is listen, tell her how sorry you are she felt that way and move on from there. Make this the thing, which pulls you together and use it to put an end to your feelings of guilt.