This song is deep. It means she is probably giving everything to her lover and he isn't even showing a bit of respect for her.
"I can hold my breath
I can bite my tongue
I can stay awake for days
If that's what you want
Be your number one
I can fake a smile
I can force a laugh
I can dance and play the part
If that's what you ask
Give you all I am"
Shes giving him everything and what does she get? Mistreated, that's what. So she stands up for herself by sining about how she's only human, not a machine.