This is another trope I really love in a size context. I think language and being able to communicate easily is one of the biggest things most people take for granted in the real world, let alone in a fantastical situation.
I’m not one to subscribe to the whole “too small/big to communicate, sound frequencies, etc.” except for the really massive size differences (like micro, nano, giga, etc.) - I like dialogue between a giant and a tiny, but when something else like a language barrier gets in the way, you’d be forced to compensate and get creative. Broken speech is usually a obvious go-to, but there’s also opportunity for the use of more physical forms of communication: signing, touching, body language, facial expressions (and reading them). By being so physical, it’s a great opportunity to emphasise their size differences: how closely the giant has to focus on her, or how big she has to make her movements; both the giant and tiny’s perspectives on their interactions and each other’s features.
Like with other tropes, it’s a very flexible one. It could also be applied to situations where either the giant or tiny is mute (maybe both!). One scenario I had I mind involves both giant and tiny being unfamiliar with each other’s language and there’s no easily accessible translator (maybe both peoples are isolated from each other, maybe one is other-worldly, etc.) And they both slowly pick up and learn from each other as they spend more time together. As a point of tension, maybe the giant is able to find another giant who can help, who is a bit more fluent than he is, but they end up making the tiny really uncomfortable. Being unable to understand, he doesn’t catch a lot of what the other is saying, but he notices something off about the tiny’s body language and gets them out of there.
From a creative/author perspective, I think it’s a fun little project. Personally, I’m not fluent enough in another language to make it reflect the real world, and I’m not invested enough to invent a language (let alone two) as an alternative. Instead, it would switch between POVs, with the other person’s dialogue being presented as garbled symbols. The POV character is able to catch the occasional word, with dialogue getting more coherent over time as both of their vocabularies grow. And throw in accents, for good measure 