I would very much love to do this and wished I had her apply for OWP from the get go but her visitor status will expire in April. I am worried about if the OWP application takes a while and it's also possible that she may be denied OWP but by that time she has either passed the 30 day minimum required to extend her visitor status or her status has expired then it would be problematic or am I missing the point?
The OWP app takes 3-4 months. It will not be denied. The 30 days is a suggestion, not a requirement. She can extend her visitor status up until the day it expires.
You are seriously overthinking this and worrying for nothing. Just apply for the OWP ASAP.