So it seems like this guy likes this girl who is basically using him. She's a burden on him, gives him grief with the mischievous/rebellious way she acts and the fact that she uses him for money. He stays with her despite this because he genuinely likes her. It also seems like she comes in and out of his life, like she's not always around ("I never knew just how much I'd missed her").
But when she is, he's happy to see her yet at the same time sad maybe because he knows she won't stick around long; she's just there to use him and he lets her 'cuz he's probably in love with her. For him, she's the very picture of sadness with her "long blonde hair and her eyes of blue" because she's the person he loves but can't have since he knows she doesn't love him back.
So it seems like this guy likes this girl who is basically using him. She's a burden on him, gives him grief with the mischievous/rebellious way she acts and the fact that she uses him for money. He stays with her despite this because he genuinely likes her. It also seems like she comes in and out of his life, like she's not always around ("I never knew just how much I'd missed her").
But when she is, he's happy to see her yet at the same time sad maybe because he knows she won't stick around long; she's just there to use him and he lets her 'cuz he's probably in love with her. For him, she's the very picture of sadness with her "long blonde hair and her eyes of blue" because she's the person he loves but can't have since he knows she doesn't love him back.