My OCs do weird things

Where dreams come to die - Petalei's backstory

"Petalei, your majesty!" Called the young brother, holding a letter. The girl laughed.
"No no Aster, it's only Floressa to you. Petalei is just the family name! Even though everyone calls me it!" He giggled a bit.
"Okay then, but look at this letter! Mother wanted me to give it to you!" She opened it and skimmed.
'Dearest Floressa Petalei,
You have been selected to be queen... Amaryllis will rule when you die... No marriage...'
"I'M GOING TO BE QUEEN?!"
"Yes." Called Carnation, the older brother.
(Meanwhile with Princess Amaryllis)
"THAT WHORE STOLE MY CHANCE AT BEING QUEEN?!" Yelled the envious princess out into the woods. She was infuriated that stupid Petalei got to rule! The Floraschius Kingdom needed a GOOD RULER! NOT A QUIET, AIR-HEADED PRINCESS!
"Are you alright, dear?" Asked an old woman.
"NO YOU- Oh wait, princesses cannot yell... No. Princess Petalei is becoming queen before me." The woman chuckled.
"And there's no way to stop her?" Amaryllis looked at her with shock.
"H-How can I?" She gave her a teabag with a big green seed inside of it.
"If she digests this then she becomes a plant monster! It's the only way to stop her, isn't it?"
"Plant... Monster?"
"Of course! It's a curse I made, if the princess were to drink a tea with it, her ceremony will be in ruins! If she even makes it, of course. The seed will permanently attack to her lungs and cannot be removed. If you're lucky, it will go into her heart instead! What do you say, dear? Do you wish to be queen?" Amaryllis nodded and returned to the castle.
(3 days later...)
"Congratulations, Petalei! I'm so proud of you!" Amaryllis forced a cup of tea into her hand.
"Thank you, Amaryllis. I've seen the crown, I'm so excited! And... What is this?"
"Oh, that's a tea I made for you! When is the special day?"
"In 12 days. And thank you, I'll drink it now!" Amaryllis nodded and closed her door. Petalei was left in her room. She unknowingly drank the tea. Every. Single. Drop.
(The seed rolled down into her heart, rather than onto her lungs.)
The next day was going normal until the princess felt sick and excused herself from dinner. She had chest pains since she woke up and also couldn't breathe well. She ran to the sink and looked at her mouth. And her neck.
It looked like there was bumps in her throat, her tongue was sensing plants...
And she coughed up a daisy.
"*COUGH* W-What? A daisy?" She was stunned, how did that happen?! That's not normal! Petalei picked it up and threw it outside.
(As weeks passed, flowers kept spurting out. And when she was being crowned...)
"I now announce Princess Petalei as our new qu-" The old man was cut off by a loud cough. Blood and flowers went flying out, vines bursting through her skin. It was a bloody mess and civilians were petrified of her. Even her family.
"... What..." Muttered her mother.
"W-Wait! I can explain-"
"You're exiled."
"W-WHAT?!"
"You're not my daughter. You're a plant monster. Leave my kingdom now." The knights all withdrew their swords. Petalei teared up and left, going really far until she blacked out. And when she woke up, she felt stiff. She was completely restricted by vines. And she looked just like a monster.
(As time flew by, she accepted she would never be the same. So she planted a castle to call her own. But deep down, she swore to forget her old home...)