how i see percy and thalias relationship:
when they first met, percy was the first and only person to help thalia at first. hes the one who instantly worried about her and called to people to get her nector or ambrosia or just any help, we dont know how thalia felt about this because its never seen, but it wouldnt be a stretch to assume she would at least be grateful for this, as not even the girl she basically raised helped her (no shade to annabeth, but percy did help thalia before she did)
we dont see them interact for the rest of the summer, and so the next time we see them theyre at odds. everyone cares more about thalia than percy, even percys closest friends listen to her more than him
for a lot of the quest theyre on together they dont get along very well, but there are a few moments that show they, or at least percy, are about the other. the main moments that come to mind are when percy found out about thalias fear of heights and when their car got struck by lighting and thalia thought it was zeus who was doing that even with most people caring more for thalia than percy, percy still worries about and cares for him (which tho really isnt ooc, he cares a lot)
the sword of hades is possibly the best we see of their relationship (and with nico) and it shows that 'hey. they may not be best friends. but they can get along and do care for each other', its especially clear with thalia worrying over percy when he got posisoned and fell into the lethe, and percy shows this when he defends thalia (and nico) when melione is manipulating them even after that quest, when they could just go their seperate ways, they go out to eat together simply because
them caring and worrying about each other is also shown (albiet a bit less) in hoo, with the hunters, a group known to hate men, are activley looking for percy, most likely from thalias orders
in my mind, these two do get along, in an interesting way at least they mostly worry about each other, and the main reason is becasue theyre so similar. in a lot of ways, they are really similar. im not gonna list the reasons, but the main way im thinking of is their past and their fathers
thalias mom was drunk and abusive and percys step father was the same, they were also both outcasted (in different ways) at camp half blood and seen as Other, and they both have a lot of weight on their shoulders because theyre their fathers children
i can see them venting and trauma dumping to each other as the foundation of their relationship, they can complain and vent to the other without fear of judgment because the other gets it in a way other people cant, and they can explain their fears that relate to their fathers domain and their childhood abusers because they get it
i get why some people make it so they dont get along, or at the least, make thalia not really like percy, but that just doesnt fit in my mind thalias first introduction of percy was him worrying about her before the kid she kinda raised did, hes also the first (and possibly only) person that knows about her fear of heights, and him promising to never say anything about it then keeping his word definitely helps how she sees him, i just cant really see them not getting along
i see them as siblings who interact twice a year and cause chaos together or thalia leaves the hunt and moves into percys cabin
either they see each other almost never or almost every day
these two care about each other and vent and complain to each other because no one else will get it and they sneak out at 2am to get shitty fast food and to vandalize police stations
yall dont get them like i do