STTGL's pilots will never try to attack Yuki's existence outside the space-time continuum since they'll never think of doing it while Yuki's physical body is in front of them. Since they won't do this, STTGL has no way to kill or restrain Yuki and have no way to win the battle.
Whether it would take a long time or a short time, Yuki can win by stealing spiral power from the STTGL pilots. Or she can just outlast their spiral power. They have a finite amount as shown by even Simon getting worn out when against the Death Spiral Machine. I don't really remember how long it took for Simon to start to run out but I don't think it was all that long a period of time. Yuki can also disrupt "data links" which would let he disrupt the flow of spiral energy through out STTGL or just outright hijack the movements of parts of it. At the same time as this, she can disrupt the pilots through that paralysis thing I mention before. Even if you think they can break through it, it's more spiral energy they have to waste on defending against.
1. She can't steal their spiral power as I doubt she can even affect them while they are in their super spiral universe (think Haruhi closed zone only they will actively fight her off unlike Haruhi who is a sitting duck basically unaware of her abilities / what she is doing. There have been many cases where the crew accessed spiral power when it was supposed to be literally impossible / spiral power "not being in the area" or whatever. They can literally create stuff out of nothing.
2. They don't have a finite limit of spiral power. Spiral power in and of itself is beyond infinite and based on willpower. Simons willpower is infinite by the end.
3. Paralysis thing has been discussed its not going to work. The space within STTGL is basically its own closed zone ' super spiral universe (states by creators of GL) where the pilots are literally beyond god mode within. etc
--
XBL GT: Demon Ninja X2
"There comes a time in every man's or woman's life where they have to make **** up to cover their ass." - Hazama