My cat sounds really weak and sick whats wrong with her?

I was sitting in my room with my puppy and all of a sudden my cat, Tinkerbell, came into the room and she sounds really weak. Her meow is really sickly and weak sounding. My mom said that Tink had a hair ball that she can't get out and she wants to know if it can make her sick. Well can it? She is sitting in the corner, in my room and she never does that. She usually stretches out on the bed with me.