Speaking of boundaries, I agree with @Voltekka about Keith being a fairy king and thus being by principal divorced from human social norms and customs—namely, to him, wouldn't be logical for Tiarose to bail on a "weak, mortal, human prince and accept the honor of being chosen to be his immortal fairy bride?" That's very much in character for a fairy king of legend and fantasy. That said, it doesn't make it a "healthy" and independent relationship for her.
Likewise, boyfriend didn't even ask what Tia wanted and just decided for her, all while scaring her and nearly killing her along with doofus.
As for Aqua, if I were in Tia's position in the story with my current memories, I'd likely not have had the "damsel in distress routine" going, I mean, she's totally acting a culture trope for these sorts of comics, the purity and vulnerabilities that were popular in past culture, got tossed, but somehow are making resurgences as though men & some women want folks to crawl back into their prospective proverbial boxes (this is worse by far than those old comics from way back in the day—at least, they had consistency & the women weren't so foolishly weak—they just "pretended" to be in order to con the men folk in order to survive, but when opportunity struck, they put them firmly in their place. Not here it would seem.
Also, the harem bit doesn't follow. It's a nice attempt, but it doesn't resonate. If she'd threatened to walk and they caved to her boundaries, cool! But, in this case, no, she's depicted as utterly weak and feckless before the MLs.
Where's your backbone and grit, woman‽ Where's the, "I'm leaving! If you insist on fighting like children, attempting to steal my agency, then I want no part of either of you! I'm done! [Exits stage]"
Had she done that and the pair caved, then turned harem—fine. But, she demonstrated absolutely no agency and it's rather repulsive—particularly without context. I'd at least like to know why. =P