Good god, how did you survive! The developers aren't that mean -- you were supposed to have both Cat and Swallow from Chapter 1 on!
*snicker* Too true!
BUT, you don't learn that she's potentially untrustworthy until Chapter 3. In the Prologue, when she gives you the formula, she helped to save you. They're talking about his recovery, and he says, "I owe that to you, Triss." She asks if he remembers anything, and he says that he remembers swordplay and adds, "I feel a bond when we speak. I know you were important." So Geralt would take and use the potions she gives him in the Prologue. ;)
Hmm... turns out I do have the Book of the Swallow now, in the new game. It has the three potions I most missed first time.. Blizzard, Cat and Swallow, heh. I wonder what happened to it the first time around. "Ah, I can sell this for money!" probably..
And well.. I had three Swallow potions that I treasured.. only used them when I really, REALLY needed it. For the mundane healing, I just ate food or meditated for a bit. It certainly got a LOT easier though when I finally learnt how to make Swallow.
Yup, Geralt for sure trusts her in the beginning. But one thing I wonder - did Geralt hear the conversation that Triss and the mysterious Mirror Woman had? Was it just shown to the player? Geralt never implies in any way that he heard it... only that he heard Triss saying something to the mirror.