Answers
Most likely due to the fact that Kurt was a Pisces.
“She eyes me” means she was looking at him.
“Like a Pisces” In the sense that Kurt was a true Pisces, all of the charactreistics associated with that sign, he embodied, and she was noticing them.
“When I am weak” Kurt was suffering from severe heroin addiction at the time, and was weakened by it.