Whatever you do, don't play the part of the "opposer".
JWs are indoctrinated to expect "persecution" or opposition from non-JW family...and there is a very low-bar for what constitutes this in the JW mindset. When, in their perception, they receive "family opposition", it reaffirms the belief system. It can also cause the "backfire" effect and make her more entrenched.
One of the three grounds for separation is "spiritual endangerment". I've seen the "spiritual endangerment" card played, in some cases, encouraged by the elders.
I'm sure when she went out in field service, she told her car group about this, and they were there to support her through this 'trial'.