nope ! it’s canon that kairi can’t remember anything from before she arrived at destiny islands, & i’ve actually expanded on it slightly in a headcanon ( found here ) which i will definitely be rewriting some time soon. the way i see it, is kairi’s memories of radiant garden & her early childhood are still very much alive & whole. they still exist, they have not been broken or disappeared. it’s more like… they’re resting dormant within her heart. with the trauma she underwent just getting to the islands, i headcanon that it was cause of lack of oxygen to her brain ( possibly not though, there may be a much bigger, more plot based reason behind it but i’m just going with what seems most sensible atm ) that caused her amnesia. she can’t call upon these comatose memories, simply because they are so thoroughly borrowed into the depths of her core, but i feel like, since they still are very much present, they still have some sort of impact on her ? 

for instance, smell is the sense most closely related to memory, right ? i feel like if she were to smell aqua ( seeing as how everybody has their own distinct scent ) or maybe the flowers at radiant garden, that it would spark some sort of umm… well, it would act as a catalyst, essentially. her memories would kind of begin to surface & poke at her, becoming less & less lost amidst the labyrinth of her heart. at first she’d start dreaming her memories, then as her curiosity grew, she’d begin to maybe search out the place she saw in her dream – more specifically, that little courtyard where she was attacked by the unversed, where aqua saved her. eventually, everything would just flood back to her, all at once. she’d remember the unversed, the flowers, miscellaneous sights & sounds of radiant garden, & even aqua. 

i feel like that would lead to kairi really urgently seeking out aqua too tbh ? she’d be so bent on finding her & thanking her. after all, aqua is the sole reason kairi even made it to destiny islands ( the protective charm she casts on kairi’s necklace that, one day when she’s in trouble, would bring her to the light of someone to keep her safe ( that being sora, in my eyes ) ). she’s also the sole reason kairi has the gift of wielding a keyblade, seeing as how, during their meeting kairi accidentally touched aqua’s keyblade, which preformed a keyblade inheritance ceremony. so… idk i feel like kairi would just have a lot to say to aqua. she’d want to make sure she’s okay & would want to return the favour somehow. 

tl;dr – no, kairi can’t remember anything about radiant gardens, although the memories do exist, they’re just lying dormant within her heart & are currently unreachable.