So my frog started burrowing again..how long to leave her under?

[GrifTheGreat]

Yep completely normal. Just do as HerpGuy and Lija have said and do check on the frog every other day or so just to make sure all is well.

[GRABibus]

My female went out of the substrate 1 month and half since October. You can imagine how long they can stay under the substrate.
And if your frog is fearful (As mine), she will go more than the others under the substrate.
What you have to take care periodically is that the frog doesn't poop under the substrate and stays in the poops ! This could create infection.