...done amazingly well to overcome those nerves.
As stated you are as likely to have a first solo have to divert because of runway closure as you are to have unforecast fog roll in.
In 30 years of flying I have never heard of a first solo having to divert have you?
Yep absolutely agree. As I said, she doesnt sound unduly nervous (any more). That's one of the great things about learning to fly - for many people it is as much about whats going on in your head emotionally as it is the actual ability to do it well.
And no I've never known a first time solo student have to divert to another airfield. I have known one have to land on an alternative runway though.
And to the OP - you're clearly doing really well and asking good questions. Trust your instructor and pay attention to what s/he says before the flight (it will be just a few points to help it go well)
Best wishes
H