These waver when married life with Diego turns out to be hard. Lupe and Diego's children live above them and continue to be involved in Diego's life, which bothers Frida. Diego often comes home smelling of another woman, after having sex with his art models. Despite Frida's resignation to the fact, she is still repeatedly hurt. Diego's art is becoming world famous, and he is offered an exhibition spot at the new Museum of Modern Art in New York. Diego and Frida go to the United States together, living the exciting life of New York socialites for a while. Both Diego and Frida have love affairs in "Gringolandia". Frida becomes pregnant, and despite Diego's worry for her health, decides to try for the baby. She soon has a miscarriage, which causes her a great deal of pain, but which also inspires many of her paintings, which are grotesque and pain-filled. Diego is asked to paint the mural "Man at the Crossroads" by Nelson Rockefeller, which promises to be a huge success, but when Diego paints Lenin as a central figure of the mural and refuses to compromise his communist vision and change it at Rockefeller's request, the work is taken down. Frida's mother dies back in Mexico, and the two painters return to their home country. Here, they live in two separate houses, connected by a thin bridge. Everything is going well until Diego has an affair with Frida's younger sister Cristina, which Frida perceives as a true betrayal. She leaves Diego, and cuts all her hair off, which inspires the painting "Self Portrait with Cropped Hair", in which she sits in a chair with her hair all around her on the ground. Her sense of betrayal continues for a long time, until one day Diego approaches her and asks her a special favour: Leon Trotsky has been granted asylum in Mexico, and Diego would like to welcome him with her. Frida agrees, as Trotsky is one of her greatest heroes. Trotsky and his wife Natalya arrive and settle in to live with Frida and Diego in the famous Casa Azul. Frida and Trotsky bond through their suffering, spending time together, climbing the pyramids of Tenochtitlan. This leads to an illicit affair between them. This does not last long, however, as Natalya finds out and demands that the Trotskys leave the Casa Azul. When Diego finds out, he is extremely jealous and hurt.
The next event in Frida Kahlo's life is an invitation to Paris for an exhibition. In Paris she has many affairs and much artistic success, but she writes to Diego often and realizes how much she loves him. When she returns, he asks for a divorce. Soon after, Leon Trotsky is assassinated. Rivera is a suspect but because he is absent the authorities arrest Frida, and she spends a few days in prison being interrogated. Rivera pleads with President Lazaro Cardenas to get her released. Following this, Frida, who is living in the Casa Azul and painting, has an increasing number of health problems. Her toes are amputated because they are gangrenous, and the pain in her back and pelvis becomes so terrible that she is often in a wheelchair or bedridden. Diego and her remain friends, and eventually he asks her to marry him again. Frida's health becomes so bad that she cannot leave her bed. In order to be at her first solo exhibition in Mexico City, she is transported in her bed to the venue. Soon afterwards, in 1957, she dies. Shortly before her death, she writes, "I hope the exit is joyful - and I hope never to return - Frida". The final scene shows her bed flying up into a blue sky and being engulfed by flames, as she lies smiling peacefully on the pillow.
Frida is filled with the colourful symbolism and traditional Mexican culture that characterize her paintings. Often the scenes of the film morph into paintings in Frida Kahlo's style, showing the direct inspiration that the film takes from her paintings. The colourful traditions of Mexico fill the scenes of Frida: the skeletons and candles of the Day of the Dead ceremonies, the mix of Catholicism and indigenous superstitions, the incessant consumption of tequila and traditional Mexican food, and the constant traditional Mexican huasteca and corrido music. Just like Kahlo's paintings, Frida wears colourful Mexican garments and has pet monkeys and chihuahuas. But Frida puts a brave new twist on these Mexican traditions, with her radical political ideology, her sexual liberty, and her modern surrealist art. Frida contains a combination of the traditional notions of Mexico as well as very modern, very liberal Mexico. While Diego is a typical machista, with his constant philandering and jealousy, Frida is not the image of marianismo, with her open bisexuality and her own fierce independence. While Frida's family portrays strict upper-class Catholic ideals, the art scene in Mexico City is liberal, modern, and radical. The modern Mexico, however, is not anti-traditional; it relies on tradition as its foundation, like Frida's art. Mexico is not only the inspiration for Frida's art, it is the fertile soil which allows her to grow, it is her home and what she lives for. Frida's great sense of national identity and pride show Mexico to be a vital, inextricable part of her. Frida is Mexico and Mexico is Frida.
When Diego Rivera and Frida Kahlo go to the United States, which they call "Gringolandia", they are surprised by the American way of life, by the immense ambition of the people, the success. Living in a snowy New York apartment, Frida is unhappy. Her miscarriage represents some kind of inner damage done by life in America. Despite the grandeur and modernity of the United States, Diego and Frida do not belong there. Their communist ideals do not go well with the opposing capitalism of the New York elite. In order to stand up for their beliefs and remain themselves, Diego and Frida must return home, to Mexico. For Diego, Mexicans are "as dumb as mules", and he claims to hate them, yet Mexico is his home. Diego and Frida and the other Mexican intellectuals are few compared to the United States or France, where there is true economic and cultural development. However, in the end, Mexico is the food for their minds, and what gives meaning to their lives. Frida's greatest pride is to have an exhibition in her home country, Mexico. It is her and Diego's home.