They issue a maximum of 300 permits a day so you will see lots of hikers all along the trail. And your fiance will likely not get lost. If she is unsure which direction to go at a trail junction she should not have to wait long for the advice of another hiker. If she can make it to the top of Nevada Falls the steepest part is over (aside from the cables). If she can continue from there up to the subdome she could wait for you there. There will be a Ranger there checking permits.
