So 'Thorne Princess' by L.J. Shen, that's the one. The central figures are obviously the princess herself, Elara Thorne, and the bodyguard, Holden Lockwood. Their dynamic is the engine of the whole book, with him being this gruff, stoic protector who's seen too much and her being a royal brat with a lot more pain underneath than anyone gives her credit for. I thought the way Shen wrote their push-and-pull was sharp, even if some of the 'I hate you but I want you' dialogue felt a bit familiar after a while.
Outside of them, the supporting cast is fairly lean, which I liked. Elara's father, the King, is a distant, demanding presence whose approval she desperately craves, and that need really shapes her. There's also a childhood friend or a potential suitor type, I can't remember his name exactly—Roland, maybe? He serves as a contrast to Holden, all polished manners versus raw capability. Honestly, I found myself more interested in the quiet moments where Holden's past or Elara's isolation leaked through than in the big dramatic set pieces with the side characters.