The four phases of Star's Princess Song represent her relationship/association with the four Card Suits.>Mewni's Own Sweetheart - Diamonds/Queen Moon
Star thinks Moon wants her to be someone she's not and act like a proper Queen, which is only half true. Moon does love Star and appreciates her individuality, she's proud when Star finds a unique solution to the conflict in "Game of Flags." She just wants Star to learn some self control and understand she has a duty to perform, which Star doesn't get until it's too late and Moon has to spell it out for after the fiasco of her Song Day.>Rebel Princess - Spades/Queen Eclipsa
"Weaving magic like a born spellcaster, wreaking havoc like a natural disaster" with her name in lights and Ruberiot wailing "HAIL TO THE QUEEN!" This is Star's fantasy, all of her pride and desires, and one of her biggest wants is to be a "rebel princess" who flaunts tradition and doesn't take shit from anybody, just like her "bad girl" grandma Eclipsa.
Star knows she has power, she likes it, and sometimes she's okay with hurting people who get in her way. This doesn't mean Star is about to jump off the morality cliff into darkness, but it's a big red flag for more temptation.>Royal Secret - Clubs/Miss Heinous
Star probably wanted this part to show how she's flawed, but it doesn't really say anything about her at all.
What it does say is that the Royal Family has dark secrets and enemies among the "forces of evil." Star herself has a whole closet.
Heinous and St. Olga's embody this, her probably being a "black sheep" Butterfly and St. Olga's probably being founded to stop another Eclipsa.
Expect more Royal Secrets to be revealed and bite Star in the ass in the future.
Like, you know, Eclipsa.>True Love's Spell - Hearts/Star Butterfly
The irony of the whole thing is that Star wanted her song to show Mewni "the real Star Butterfly," but it turns out the only part that's really true to herself was written by Ruberiot alone.