Speaking from experience I wouldn't put her I a any kind of breeding net or breeding box as it really stresses out the fish and can cause issues with her giving berth so what I would suggest is lots of live plants or fake ones work to basically just lots of good hiding places for the fry.
Once the fry are 1 or 2 days old there big enough that the parents tend to leave them alone and once my platys had several batches they just kinda lost any interest in eating even newborn fry.
Anyways that my two cents worth on that so good luck with however you do it