Hi Laurie,
To me it seems like a no brainer: She needs to sign up with AAISP. Static IPv4 and IPv6 IPs for all, they can bond the lines together too at no extra cost, you're just paying for two lines rather than one.
The support is absolutely 1st rate.
They also have great monitoring tools so if there are problems with the lines or they deteriorate over time this should be clear using their monitoring platform (as a customer, you get access to a portal to see the health of your own lines/services).
This might be slightly overkill; http://aaisp.net/broadband-office1.html
I work from home, I have this, it works great: http://aaisp.net/broadband-home1.html
You could just order two home::1 packages and ask for them to be bonded.
You can drop on their IRC channel (or pick up the phone) and ask the tech guys and customers on IRC any questions you have about the service before you buy.
Most important to note (I think) - is that there is no other ISP in the land that can kick BT's backside like AAISP when there is a line fault and not an ADSL service issue and BT are playing hardball. AAISP will throw the book at them, they have a lot more weight as a wholesale customer of BT than you or I do as an individual user.
I can't rate them enough (I don't work there or own shares etc ;) )
Cheers, James.