The business plan at 1&1 is a shared server:
http://order.1and1.com/xml/order/Hosting;jsessionid=67436E6E3CBD83EAA38804D59A58160E.TC61b?__frame=_top&__lf=Static
hence the no support for RMS on it.
She would need to upgrade to a VPS at 1&1 before they will support the RMS. Business server is $9.99 a month, VPS1 is $29.00 a month.
This is where you have to make a choice ling, you can stay with 1&1 on the Business server at $9.99 a month and pay someone $5-$10 a month for use of an RMS (plenty offer them, like Dosdawg, JTadeo and so on) or you can upgrade to the VPS1. $29 a month is one of the lower prices I've seen for a VPS.