I have created a workbook and saved it on my colleagues connected computer. When she tries to access the file, she can only get it in read only. She is asked to save a copy.

I can access it and save it myself no problem. I have gone to tools and share workbook. I've also ticked "allow changes by more than one user at a time". Is it a case of having to save and then merge it? Any insights would be great as can't seem to find any help elsewhere!