Apparently not: The brand-new Homepod Mini doesn't support Bluetooth audio, either, although the BT antenna is inside for setup purposes & handoff feature. Walled Garden Must Be Maintained At All Costs. (Edit: Will some future Homepod ][ have a battery and support Bluetooth audio? I wouldn't take bets...)And Apple are seemingly happy to improve a products capability over time, which they will be the HomePod line.
But to your sister (and to me) original Homepods are pleasant and unostentatious -- way less fancy but a charming shape and surface, relative to the Balance -- and they sound OK, even as compared to the Beosound 1. Alas, tone controls are not supported at all(!) which makes people complain about the bass boost their auto-mics apply. Worse, personal login with 2FA is required, even to act as an open Airplay endpoint -- there is no "speaker only mode" to not use Siri & not control your Homekit devices. (Edit2: Back on topic: Certainly she chose Homepods over the chunky lunch-pail Beolits! Regardless of whether or not she wants to take them outside or talk to them...)