kk while i LOVE laines flower symbolism (+ my user is literally flowersforlaine lol) i also think they're NOT her motif and here's why:
other than the flowers in her room as decoration and the flowers she gets for performances shes only really interacted with them TWICE to date.
the 1st being in season 1 obvs when she was with smoke, 1st when she asked them out and gave them flowers and then l8r smoke gave her flowers (AND THE TRAIN STATION SCENE OMGGGGGGGG AAAAAAA) plus the flower notebook ofc!!
then in season 2 when river asked her out w a rose- but SHE LOST THE ROSE AT SCHOOL!! only found it some days l8r when it was all withered and dead!!!
so here i present: flowers r not LAINE's motif they are SMOKE's motif. and river giving laine a flower represented how they were trying to be like smoke was to laine, and laine accepted but forgot the flower in the theatre anyway, the same theatre she used to hang out with smoke in!!!!!