You cannot mount an NTFS volume in two places. This is by design to avoid FS corruption. You can, however, make a symlink from one location to the other.
Let's say you mount it at
/mnt/ntfs1 and want to make a second mount point at
/mnt/ntfs2. You can symlink
/mnt/ntfs1 as follows:
sudo ln -s /mnt/ntfs1 /mnt/ntfs2
Note the order in which the directories are given. The one where it is successfully mounted is first, and the place where you want to "mount" it is second.
Note that this is imperfect as using
cd .. in shells will cause you to work within the wrong copy, but for file management programs, this should work, with one caveat, from here:
NOTE: There is the danger of a file becoming corrupted if more than one person tries to edit it at the same time.