Actually, looking carefully, neither the sweater Kayla wore nor her birthday cake include the specific colors of the LGBT flag. The sweater is missing purple and green. The order of the colors are not the same as on the LGBT flag. If Kayla or her mother actually had been intending to express solidarity with LGBTQ people, they chose poor symbols.
Actually this doesn’t matter because Kayla had already “come out.” Maybe her “gay pride” colors don’t fit your sexual dogma but it’s a lie to say that Kayla wasn’t representing LGBTQ values : https://www.theamericanconservative.com/dreher/the-rainbow-cake-girl-what-the-media-are-hiding/