Hi Dil
If she was set up as named in one company and concurrent in another, that would have caused the problem. Global users have access to all the companies listed in their Global User record, they don't have to be set up as a Person in each company. However there are more parameters on the Person record than on the Global User record (for example Location, Bonus, Number Series) so if you are using these then you will need to set her up as a Person in each company as well. If you do this, you must set her up with the same user type in each company (i.e. all named or all concurrent).
I believe in your case, just removing her Person record in the second company may have fixed it.
Hope that helps.
Paul