The speaker feels caught between wanting to be noticed and refusing to be someone else to get it. The poem's pattern is simple: when the speaker pretends to be happy around "you," that person pays attention. When the speaker insults someone else, that person pays attention again. The repetition of "You pay attention" makes it sound like the speaker has been watching this happen and drawing bitter conclusions.
Then comes a sarcastic turn. If attention only arrives when the speaker is fake or unkind, maybe they should become "a happy bitch" and get it that way. The tone is angry and hurt, and the stumbling repeats ("Pentend," "into, into") make it feel raw and unpolished, like words spoken in frustration. The last line pushes back firmly: "there's no way I'm changing just for you." The mood is defiant but also a little sad, since the speaker clearly still wants to be seen, just not at the cost of being themselves.