This was a search warrant issued at the time of her arrest (within less than an hour according to the article). The woman subsequently pled 'no contest' to the charges and unlocked her phone.

In short, this doesn't mean this is a settled issue - none of this has been tested in court.

Could she have refused and held in contempt for 48 hrs? After which she could no longer be held in contempt?

Legal niceties take much longer than this. Once 48hrs is passed your fingerprint is useless to unlock the phone. At that point there is nothing they can do since they cannot demand you give them the code. A finger is part of your body, the passcode is only in your head.

Which is why I'm still wondering how this decision even helps...

This wasn't a decision - it was simply a search warrant that included the demand. It's not a legal precedent or case law...