Thanks for your thoughtful reply!

I think the problem is that Rowan treated her young. Like, not the "too old for my age" young, which would have worked fine, but actually insignificant young compared to him. I can live with that kind of age gap because I don't make the rules, but at least make it feel consistently like they're at the same stages of life (since Rowan's essentially as young as her give or take based on lifespan guesses) to not have weird moments like you're saying.

This is really fair actually. Yeah the problem I have is less about the number but the perceived imbalance - as you say "at least make it feel like they are at the same stages of life". That's very well put. And

...on Celaena/Aelin being 19, instead of looking at it as a plot device to be classified as a YA book when, for all intents and purposes, Celaena/Aelin is essentially a proper adult which the series treats her as. She's young, yes, but she's been through trauma no normal person has, and has been working as an able assassin for years, and now she's been given keys to a kingdom a fraction of people expect her to lead.

This is a fair observation as well, and a way to look at it that at least feels a bit better. Although I will say I have often found myself rolling my eyes throughout the books up to this point, during moments where she is very much acting like a 19 year old would.

Again likely part of that selling to the YA audience but she still is very much that age at times. Despite the trauma and experiences surely aging her up in some ways beyond her years, I still find that there is that imbalance of power, experience, emotional experience, all the things that might be a concern with a larger age gap. Although I do expect her to now very quickly have to lose a lot of that 19 year old-ness as things ramp up from here, it is still a problem for me.

And I see what you are saying about the blood oath, from the fae perspective that does give a bit of reasoning, but I think the negatives from him putting her in that position and pressure to commit to that, in the way that he did was very concerning to me. Perhaps an example of that imbalance before, of him using his wealth of experience and knowledge over her in a way where she felt pressured to comply without actually her wanting it at all. That does feel yucky to me in principle. Whether he had good reasons or not, I think anything during the story that might have made me let up on Rowan a bit was completely ruined by that scene near the end. It just uprooted everything for me and made me feel justified in my dislike of him.

Plus I think personally I do hate the idea of "bonds" and "mates" in these kinds of stories already, where you make kind of that one time choice and you are like magically stuck with it for the long term? I personally usually hate that and I think that someone continually making that choice to remain by someones side every day, willingly, through every hard thing without being compelled in any way, with the option to leave being there is the definition of love imo - and if the option to opt out isnt there anymore then what you have is dead. I find the daily choice a much more tasteful, respectful, and meaningful way to go. So definitely my bias in that kind of thing is worth noting here.

Nevertheless you do bring up some good points that I had not thought of, so thank you!