Not too sure on the Hotmail question. What i would recommend though is that if your mum uses her hotmail email account as her main email account the Hacker will have access to her Emails and possibly any registration emails that your mum may have stored in her Email account.
If she uses internet banking, online credit card accounts, clubby book accounts and anything else you wouldnt want anyone dabbling with that they may have access/passwords too, she should get online and make the necessary changes ASAP.
Maybe this has already been done. Just a heads up