Can user add category without admin activate the taxonomy module for user?

HI all,

I am very new to Drupal. And I am searching for solution for my issue. Currently, I am trying to help my friend to update her website which was done by her very old lost friend ( can't reach the person anymore). And I find out that the website is actually done using Drupal. Her website has top navigation bar with few submenu. Now she wants to add another sub menu under "catalogue" menu. Then I find out from forum that theres should be a taxonomy modules installed. But the problem is...I can't see any feature to install any module. She can only update or add in "product" into category that has been created but not to create any new category. I guess should be the admin (which might be her friend) not allowed her to access. Then, how do I add the sub menu without that module? Is there any way? Perhaps like edit some files or what? I am clueless...I am very curious to know it, too. Please help.

I attached screenshot. Hope it helps

Thank you