Can someone help me find this?

It’s one of those reincarnation royalty trope. I mostly only remember the characters having a drink outside, the fl with her brother (I think?). I’m pretty sure they had blond hair. The main thing I remember is them talking and looking at each other right before the effect of their poisoned drinks hit and loosing consciousness. The (maybe) brother afterwards apologized to the fl and said it was bc she was with him, who was next to the throne and had an assassination attempt but she got mixed in.
It’s similar to “who made me a princess” and I’d like to read it again, but I can’t remember the title nor find it bc of the whole reading lists issue.
If this sounds familiar to anyone, please let me know. All help appreciated! Thanks in advance for any help!