" The shuttle would be too weak."
And yet a class four probe would make it just fine?
" Too many crewmembers would need to go with her. Etc."
It's a simple warp-capable shuttle. Nobody but her needs to go on it.
Like I said before- it's only because the writers didn't think about it.
It's the same reason why they continually forget about how casually Kirk flitted back and forth through time in TOS- because then you wouldn't have a show.