overwrite a plugin function in functions.php

Question

need to customise a plugin function but would rather not edit the plugin itself so updates wont remove the custom changes.

function iss in a class called UserAccessManager and the function is;

public function showGroupMembership($link, $postId)
{
    $uamAccessHandler = &$this->getAccessHandler();
    $groups = $uamAccessHandler->getUserGroupsForObject('post', $postId);

    if (count($groups) > 0) {
        $link .= ' | '.TXT_UAM_ASSIGNED_GROUPS.': ';

        foreach ($groups as $group) {
            $link .= $group->getGroupName().', ';
        }

        $link = rtrim($link, ', ');
    }

    return $link;
}

is this possible? OR can i affect it with a filter?

Any help appreciated! Dc.