This lad is ace as fuck
She really just needs to tell him, "Hey, I want to have sex, can you do that for me even if you're not as interested in it as I am?" Otherwise he's just not gonna get the message that she's not just doing this out of a feeling of societal expectation or insecurity, but because she actually wants to. Seems like he's reading it as insecurity in their relationship right now, and not as genuine interest in jumping his bones. So spell it out