So far as I'm aware, VNC doesn't actually involve logging in to the
"remote" system.  I use it from home over VPN to a Linux system on my
company's private network, which requires logging in at first (I use
ssh, but other methods work) to launch the VNC server session; then
afterwards, you simply connect to that session and it behaves pretty
much as if you're actually logged on to that machine directly with a
graphical interface.

I develop and maintain a Java app my company sells, and I test it on the
Linux platform this way all the time without issue.  VNC, if memory
serves, uses HTTP for its data exchanges between the viewer and server
apps, but otherwise the system you're "viewing" is more or less unaware
that the user it remote.  This is not a Java issue.  It works for me as
it should, with no Java code that has any inkling of its surroundings.

The point of all this is to say that I obviously don't know precisely
what her issue might be, but it shouldn't be related to setting the
DISPLAY variable or using xhost+ or any of those things.  Perhaps her
actual connection method is at fault (you mention rlogin).  The key for
me has always been that I initially connect via ssh, then start the VNC
server on my Linux box, then log off.  Next, I simply connect to that
existing VNC session from some VNC viewer app (most always from my
company XP laptop, but sometimes via other systems).

Lotsa luck.

= Steve =