First of all, if you are using points from two separate accounts, I'm pretty sure it has to be two reservations. Second, it doesn't matter whether you "have all her information," they are not going to let you use her account for anything...unless...
There are two ways around this that I know of. The easiest way is to have her transfer the required number of points into your account. Then you would be able to do the booking alone, and you would only have one reservation.
The other way is to have her designate you as an "associate" on her account. She can do that online and that will allow you to use her account. You would still need two reservations, I think.