The word she uses is "servants", a less loaded word that allows some ambiguity on whether she's just describing how her kin will see you as (which the Kith'rak does see you as) or if she's personally describing you. In any case, don't forget that the player character can also be a gith - so that statement wouldn't even apply to you.
You do have plenty of reasons to doubt Lae'zel since she's not friendly in the beginning and any other reports of gith are accompanied by murder. Her own actions to Zorru and her threatening to kill you in the first camp scene can leave a pretty untrustworthy impression. Shadowheart isn't necessarily wrong.
But through Lae'zel, you learn gith are mortal enemies to mindflayers, what the name of the "purification" device is, and hear her constantly reiterate that she is certain. At least judging from how you can respond to her in certain situations, it does seem like the game implies your character really thinks the gith would have a cure. By the time you realize she's naive and/or holding on to a wish and a prayer, you're already at the gith patrol.
For now I won't elaborate, but I think this is intentional and will be a theme in Lae'zel's plotline. There will probably be a lot of extra fighting and difficulty if you follow our favorite gith companion. I think if you don't have Lae in your party, you get a proper warning that you probably don't want to mess with the gith if you're low level. If you're an ok level, Astarion will say "can we kill them please." With Lae'zel there, she will run right into it regardless. And if you like this character, you're not going to abandon her. That's intentional.
Things aren't as urgent as they originally seem, and it's only urgent because for her, everything is riding on being purified. This is more her questline than the main quest.
Last edited by AvatarOfSHODAN; 10/08/21 06:23 PM.