This has been asked before and it is possible. There is software that can be installed on a BB to do this. Typically sold as teen monitoring software.
However, it could also be a case of plain old stalking. Going through her computer, logging into her account, reading her .ipd backup files, following her, etc.
She should wipe the device using jl_cmder, reinstall the OS, change all passwords on her computer, BB, cell phone account etc., and dump the guy. Once the psycho behavior starts it rarely just goes away. How do I wipe the BlackBerry using Jl Cmder? - BlackBerryFAQ