Suika's dialogue implies somewhat that she's not even using her density manipulation to turn herself big. In other words, she could go bigger.
What happened? Did I turn giant?Tower of BabelI guess I'm bigger than giant Suika now. So...this is how it feels.But there was no moon! What happened?Damn it, did she lose her humanity?Keine, is that you? Answer me, Keine!Mssss Keineeeeeee!It's so narrow here...Hey Ms. Keine, are you okay?Where is this? What happened?Ibuki Suika [Giantess Buff]