28K is also a possibility. These are US sizes however, in UK that’s 28H/30GG.
However she really ought to do a leaning measurement as well at her size, might make her a 28L/HH or more.
If she gets some bras in those sizes and videos trying them on we’d know for sure.
And yes, in the video she said her boobs were even larger in her recents shoots, so perhaps even 28M/J or 30L/HH at that time.