Orwell never says what they confronted Julia with in room 101. In the end it doesn't matter; all that matters is that room 101 contains a person's ultimate breaking point, their absolute worst fear culled from a lifetime of data. The specifics are irrelevant.
Part III, Ch. 5:
‘By itself,’ he said, ‘pain is not always enough. There are occasions
when a human being will stand out against pain, even to the point of
death. But for everyone there is something unendurable–something that
cannot be contemplated. Courage and cowardice are not involved. If you
are falling from a height it is not cowardly to clutch at a rope. If
you have come up from deep water it is not cowardly to fill your lungs
with air. It is merely an instinct which cannot be destroyed...'
The government did to Julia exactly the same thing they did to Winston - force them to betray each other by showing each of them their own, personal nightmare, the one thing that the mere threat alone is enough to break their will.
Orwell never says that Julia had been given a lobotomy (trans-orbital pre-frontal lobotomies don't leave much of an external scar). She seems to be lucid when she says this:
Part III, Ch. 6:
‘Sometimes,’ she said, ‘they threaten you with something–something you
can’t stand up to, can’t even think about. And then you say, “Don’t do
it to me, do it to somebody else, do it to So-and-so.” And perhaps you
might pretend, afterwards, that it was only a trick and that you just
said it to make them stop and didn’t really mean it. But that isn’t
true. At the time when it happens you do mean it. You think there’s no
other way of saving yourself, and you’re quite ready to save yourself
that way. You want it to happen to the other person. You don’t give a
damn what they suffer. All you care about is yourself.’
It's open to interpretation, but my own feeling is that the scar is simply left over from the "mundane" torture inflicted before room 101. She does appear to be in worse health than Winston, but I think Julia was much more "alive" than Winston ever was, so she had much farther to fall.
"What happens to you here is for ever."