This assumes that the hard drive is physically intact. Put the drive into a 2.5″ enclosure and hook it up to another Mac.
- First, attempt to open the Disk Image, by going to the new drive’s USERS folder, and double clicking on the File Vault users disk image (it should be named the same as the users SHORTNAME).  This should then cause the system to prompt for the password.  Once the password is entered, it should mount as a disk image.
- If that doesn’t work, try this use an Admin account (call it user2) to mount user1’s FileVault using the following command in Terminal :
sudo hdiutil attach /Volumes/UpInFlames/Users/user1/user1.sparsebundle
where UpInFlames is the volume name of your MacBook drive. You’ll need the password of the user2 as well as the password on the sparsebundle.
Then you should be able to access the data as normal.