Okay, I have had a few of you ask this in reviews/PM: Why doesn't the mermaid just write what she wants to say?
[The answer to this got kinda long and technical, so it will be at the bottom]
The next morning Lila woke to urgent knocking followed by two very excited girls running about her bed. "Milady! It is so exciting, you must get up!" The girl was excited, but not angry. However, Lila never wanted to leave the bed. "The prince asked to spend the whole day with you at the festival, you must get up!" Lila shot straight up out of bed. They dressed her in a cream shift topped with a long tunic with tight medium length sleeves that was open on the sides and laced up closed. The tunic was a deep dark green and has light green and soft yellow roses embroidered all around the edge.
The girls brought Lila to the main room of her suite and sat her down to do her hair while she was eating. The tray had already been set while she was dressing; a soft boiled duck egg with some warm bread and half a baked apple stuffed with pork sausage from the night before, some berries, and a warm cup of tea greeted her under the shiny dome. While Lila was eating, the girls brushed and pulled at her hair, braiding it round her head. Lastly one pinned in a dark green head cap with a cream drape hanging from it in the center of her braid to cover her from the sun while the other brought out a pair of green dyed leather slippers lined in ermine.
Lila walked through the festival with the prince in a tidy row: two guards, the prince and Lila, her escorts, followed by two more guards. The prince hardly had a moment to speak directly with Lila; nearly every booth, stall, or business wanted the prince to have a pastry or pie, a bowl of stew, a smoked sausage. Every singer sang for him, every performer wanted him to come in and watch. Lila could tell the prince was beloved by all his people and that he was very polite and tried every dish offered and watched and listened to every performance. Lila was able to try everything too, as she was accompanying the prince; she was having so much fun, she nearly forgot the ever present pain in her feet.
When they returned to the palace, Lila looked sadly at the water and her escorts asked if she would like to go down to the water. They walked Lila to a small secret cove; one Lila had not been able to see from outside. It was surrounded by high cliffs and a section of the beach had marble stairs from the lawn to the calm lapping water. The girls sat on a small bench under a tree while Lila stepped down to the water and slipped off her shoes. The cool salt water soothed her feet. The night came and Lila went to bed.
Each day was the same; Lila going about the festival with the prince. Tasting every food, looking at trinkets for sale, and watching performances with the prince made her very glad. But each night she went town to the sea for as long as she could stay and let the water soothe her pain. The last night of the festival, there was a public dance in the square. The prince had Lila accompany him to the dance, just as he had for all the other festival activities. Lila wore her dress from the feast to the dance, and though he danced with many girls from the village during the night, his first and last dance were with her.
The prince had a special riding outfit made for her, and each week she went out with him on a ride in the forest. Lila liked going on rides with the prince, for they took the pain away from her weary feet. He spent a good portion of each day with her, and each day she loved him more than the day before. The prince however, had not yet put it into his mind to have her as his bride.
Lila mourned each night at the beach. She missed her friends; she missed her father. She could never again speak or sing, and the prince was still no closer to taking her as his wife and giving her a soul. One night at the water, she looked down and saw her friend below the surface. "When your father said you had left home, I knew that you had seen the witch and you were here. I have been up each night trying to find you." Lila opened her mouth to reply to her friend, so she could see Lila could not speak. Her friend took pity on her, "I will go now, but I will return. I will tell your father you miss him greatly." So each night, Lila returned to the same spot on the marble steps where she soothed her feet, sometimes seeing a few friends or finding a small gift they had left for her.
Okay, I have had a few of you ask this in reviews/PM: Why doesn't the mermaid just write what she wants to say?
Despite Disney showing Ariel writing, there is no way they would have writing other than full on carving underwater. Books that sank with ships would probably get ruined through usage, and probably don't hold much value for most mermaids anyway, as they could never practice writing. This is why Lila's goodbye note to her father was a large fancy shell for him to find and know was from her. The story wouldn't work at all if they didn't speak/understand the same language though, so you can assume that they probably interacted more at one point in time and the mermaids may have lived a lot closer to the surface; speaking the language of the villages near them. Something happens, probably the fishing industry or lifespan jealousy or something about magic or religion pushed them away from each other. They still speak the language, because they always have. Even if it was not their first language, going along the standard 'three generations' to breed out a language [where the language is generally only spoken at home] and the mermaids live 300+ years then a generation [from your birth to the birth of your first child] could easily be 100 years. In a place where it is also spoken outside the home, it could be longer [Spanish has a 40% speaking rate for 3rd gen] so it could be anywhere from 300-500 [or more] years easily that have passed since they stopped interacting with people on land, but still use the language. Especially if they based their government/schools/farming/whatnot off of the human world, and used their words for things, and have houses full of human objects they would otherwise have no words for. So Lila could easily speak/understand the language, but she cannot write.