Can someone who has a legal guardian have a will drawn up on their own or does the legal guardian need to assist?

I would think that if someone needs a guardian they would not be considered mentally competent to make a will. If they required a guardian because they were temporarily incapacitated they would need to petition the court to have the guardianship revoked, presenting medical documents to prove they have the capacity to look after their own affairs (not a do it yourself project, it would need a lawyer). Is there any possibility the guardianship was a temporary one that has expired?

In Nevada the ward (Loved One) has been declared to be incompetent and the guardian has the final decision on nearly everything.
We have three different types or levels of general guardianship. Person,Estate,Summary Admin, Person and Estate.
So I would presume it would depend on exactly what type of guardianship has been assigned.
I would suggest you contact a certified elder care attorney for guidance. Our attorney also does wills and I am consulting him on preparing my own will to ensure continued care for my wife.