Apps2SD is built into Velocity v0.3 and Raptor, so there is nothing additional to do. However, properly partitioning the SDcard is critical, and is where things usually get foobar'd.
I cannot stress enough the importance of starting off with a completely clean install. Some important things to consider:
1. Which recovery are you using on her phone? People typically seem to have fewer issues with Amon Ra rather than Clockwork.
2. Start with a completely clean SDCard. This means to partition it as 0 Swap, 512MB ext and the rest FAT. Convert the ext from 2 to 3 and then from 3 to 4. NOTE: This process wipes everything off the card. Copy anything important off to your PC first.
3. Clear Factory/Data cache, Cache, and Dalvik Cache.
4. Connect the phone via your USB cable and copy the ROM of choice back to the SDCard.
5. Flash the ROM zip file to your phone.
6. Reboot the phone and your phone should complete setup.
7. Go to Settings/SD card & phone storage settings and check the Internal phone storage Available Space. It's usually around 103 MB for Raptor, not sure what it is with Velocity v0.3
8. Now - and this is important - re-download and install the apps she wants to use. Why not restore from backup? All I know is some apk I had was obviously eating my storage space and redownloading them fixed the issue.
Doing things this way, I have 52 apps installed and 60MB free using Raptor.
Another thing that is in Raptor, may be in Velocity also, I don't know - Gscripts. It has a script you can run that will test apps2sd. If there is a problem, it will typically tell you there is no apps2sd or it is corrupted.
I can guarantee that if you follow these steps and there's not a problem with the physical sdcard or the phone hardware, you -should- see an improvement.
I hope this helps you. Good luck!