» Fri May 13, 2011 1:54 pm
If you like Sydney, you owe it to yourself to get the http://www.fallout3nexus.com/downloads/file.php?id=9320.
It is hands down the best custom companion mod I've ever seen; a well-thought-out personal questline, FULL voicing for every single one of her dialogue options, and a companion who manages to be effective without being OP.
Again, if you like Sydney and want her to stay on, you owe it to yourself to try this. Make sure to enable it before you finish the quest, if possible; makes recruiting her easier.
To directly answer your question, Sydney will stay with you as long as you don't finish her quest; she will act like a normal companion. Still, I recommend getting the mod, though; it makes her a much better companion with the added perk of her not dying, just getting knocked unconscious.