Leo says she should have a local on-site backup in addition to using one of the cloud services. But since she's running out of space on her internal drive, she should get an external drive to have more space to work with. Since she has a newer Macbook Pro without a FireWire port, she won't be able to get a faster FireWire drive, and is stuck with the slower USB 2.0. Apple was counting on manufacturers to make drives for their new Thunderbolt port. No one really is using Thunderbolt yet because the cables are so expensive, and the drives themselves are too.
Leo suggests going to MacSales.com (Other World Computing). They have a lot of external drives, and they do have Thunderbolt drives, but they're around $1,000. Leo would just get a big 1 or 2 TB USB 2.0 drive and just use that for the photos instead of the internal drive. But she should still back that up too!