Spouse getting additional insurance while I have a HDHP-plus-one

I am a federal employee and have a HDHP provided through my federal employee benefits that covers both me and my wife. My wife is self-employed and is pregnant; due at the beginning of 2023. I was advised by a friend to have my wife get insurance on the open market just for herself in addition to my HDHP that covers both of us. I’ve found a plan I would select that has a $0 deductible. Then when we have the baby, the amount that her $0 deductible insurance covers will count towards my HDHP deductible and the HDHP will then cover any remaining amount we owe (my HDHP covers 100% of maternity after the deductible is met). After the birth, we would use the birth as a qualifying life event for my wife to drop her insurance and would use only my HDHP which we will increase to family coverage.

Running the numbers, this idea would save me $2000 and result in us having our HDHP deductible paid off for the year. However, I’m having trouble verifying that this plan will work. I’ve spoken with several insurance representatives, but they’ve provided me with conflicting information which has made me doubt if I can rely on them. My two questions are:

Can my wife get separate insurance for herself while also being under my HDHP?

Is my wife allowed to use the birth as a qualifying life event to drop her insurance?