>>537952718
Her main story is Fate/Extra CCC, so there's that, though I'd recommend playing Fate/Extra first.

If you're not gonna play entire other games, then as the other anon said, play through the main story until you can get the SERAPH Main Interlude. After that read Summer 3 (Servant Summer Festival). Those two have the most BB presence. She'll also be in next years Summer as well.

On the subject, since BB is another example of giantesses, this reminded me, having recently finished TsukiRe, I find it funny how Nasu chose to indulge his giantess fetish there in the new content as well.