The width styling is inline and set within the module template file for the GJ module. You can find the template file below.
components/com_comprofiler/plugin/user/plug_cbgroupjive/templates/default/module.php
Easiest way is to just override it with the below.
Code:
.gjModuleCategoryRows .gjModuleCategory,
.gjModuleGroupRows .gjModuleGroup {
width: 100% !important;
}
You can add the above to CBs built in CSS overrides shown below.
www.joomlapolis.com/blog/kyle/18711-template-css-overrides-made-easy