charli xcx is a pop star that makes electro-dance-pop music. that kind of music, and her, is popular with a lot of trans women

the joke is from the perspective of a guy outside a women's bathroom at a charli xcx concert "waiting for a woman who seems generally unwell" - AKA a guy trying to hit on trans women, light jab at the fact that trans women selfstereotype as dorks / basement dwellers

the guy's pickup line is just a silly nonsequitur about burt's bees brand chapstick. "you on spiro?" is him asking if she's on spironolactone, which is an anti-androgen and one of the most common hormones that trans women take in north america

i know that explaining it kills any humor in it, but it's a really funny joke to me because it's a situation i can easily imagine getting in, one that makes fun of the trans experience, but not necessarily trans people themselves (despite poking fun at the fact that the guy is looking for shabby-looking women to, essentially, ask them if they're trans). it doesn't play into the narrative of trans women as fucked up or fake women. it's just a beautiful little joke.