Artur, if she only eats "live" try adding a little more water flow in the QT. Maybe if they "bounce" around more, she may think they are live. Also, what size it your QT? I have read that garlic can be very strong and cloud the water so that the fish don't really know where the food is. Try diluting it. I am reading my Kent's Garlic Xtreme (I ran out of garlic guard, and the LFS
only had this) and it says 1 drop per 10G. Check your directions and follow that.
+++I also still want to repeat what Mike said, this does not cure ich, but studies have shown, fish treated with garlic were less prone to infection/reinfection.+++