An old saying, forgot where it comes form: "diplomacy far away, attack nearby". You need friends and you need to expand, best way to do it is to pincer your victims. I would've befriended Isabella and spited Huayna myself, but what's done is done. Hope Huayna has a Buddhist city then.
for another perspective ...
this isn't
Hello Kitty Best Friends Game[1]. this is civ4 warlords, friendship isn't forever. we're not ready to attack yet. shouldn't we partly pick our friends by how much use they'll be now ... if we think we can cultivate friendship with the other party later despite the damage done? i'm confident that S can make izzy a friend later, and i think he kind of likes the "kiss and make up" phase anyway

. plenty of time for tea parties after we make sure HC won't be a run-away tech leader. HC can be our friend for now, so that we can time the war for when we're ready. isabella wouldn't be a helpful friend IMO. getting CoL in a trade would be lovely, but it's a monopoly tech. helping in a war, i think she'd at best be a pillager, or the off-chance that HC gets distracted by her for a bit.
I looked at the map again, and there may seem to be oppertunities to trade away your health resources, even those that you only have 1 of, for happiness resources. That may be a good way to highlight the UB.
i
really like this thinking. i am a big believer in locking in available resource trades ASAP so that we don't lose the chance when they trade it to someone else. it's very much tied into the first point tho. all ongoing trades have to be considered politically, and leave you open to demands to cancel trading, which are guaranteed to gain you a - with somebody. if we trade with someone we're going to attack soon, we have to be careful of addiction to resources that we'll lose when that happens. that's fixable by whip tho (if we're not in caste). capturing and owning will of course be better than trading for it

.
also, when we learn calendar, we gain access to 2 happies when they get hooked up (+ silk with a border pop), but we instantly lose the

from the monuments (charismatic). and we know how S is about workers sometimes (S you know i love you but...). again, whip can fix it, if we're not in caste.
[1] yes i do own that game, a friend gave it to me. *giggle* we are both over 30 years old. the box recommends ages 7 to 10. big deal, it's just a recommendation! *more giggles*