Despite the fact that Maria and Tony sleep together, their relationship is surrounded by romantic terms of love, commitment, and wedding images. Later, in "A Boy Like That," Anita cautions Maria to avoid him because he "wants one thing only" and "won't kill her love," as if he had slain hers. In truth, it is she who has been doling out her love to various men without commitment.
Their encounter in the rain is purely physical. There is no deeper connection between them and they go about their separate ways with nothing more than a kiss on the cheek.
However, it is clear from Tony's reaction when he finds out Maria is pregnant that he wants to be the father of her child. This idea comes straight from her - she tells him so directly in "Maria's Baby Story." As for why she would want such a man - someone who would use her and then leave her - we can only speculate. Perhaps she saw something good in him that she wanted to hold on to. Or perhaps she was just looking for a way out of her life at the time and felt like taking advantage of his kindness.
Whatever the case may be, she sleeps with him and then leaves him after telling him that she is pregnant. It is clear that she does not love him anymore and there is no chance that she will ever come back.
The next day, Tony pays a visit to Maria at the shop, where they perform a romantic wedding ceremony amid the clothes dummies (One Hand, One Heart). Maria forces him to swear to put an end to the war between his gang and her brother's. Then she gives him a ring that belonged to her mother, who died when Maria was young.
They go back home, where their families celebrate with them. Later on, when everything has quietened down, Tony tells Maria that he must leave now but will return soon. Before he goes, he kisses her goodbye and whispers in her ear: "I love you".
Maria stays behind to close up the shop but is soon joined by her father, who wants to know if she has found out anything about the murder of her boss. When Maria says no, he asks her not to worry about it. Suddenly, there is a knock at the door and it opens without warning - revealing a gun pointed at the father! A robber has broken into the shop during the party and is now holding everyone at gunpoint.
The criminal makes his way towards Maria, who is terrified but doesn't move. Her father tries to stop him, but he shoots him dead too. The criminal then turns his attention to Maria, but before he can shoot her, a police officer walks in and arrests him.
Later, after the dance, while the gangs congregate at Doc's drugstore to select a location and weapons for their rumble (a gang fight), Tony pays Maria a visit on her apartment's fire escape, and they pledge their love (tonight), promising to meet the next afternoon at the bridal shop where Maria works. When Tony leaves, we see that he is wearing a ring designed by Maria.
Now, this isn't exactly how it happened in the movie, but it's very close. The scene was added because the filmmakers thought audiences would enjoy seeing Tony and Maria together before all of the violence against them. They also felt that showing the relationship between these two characters more fully would help explain why Tony would go against his family during the course of the film.
In real life, Tony didn't go to prison until years later, when he was already an old man. And even then, it wasn't because of any crime he might have committed as a young man, but rather because he refused to testify against John Gotti.
However, despite being significantly altered from its original version, this scene is actually based on a true story. The character of Tony Camonte was based on real-life gangster Anthony "Tony Blanco" Bozza, who was born in Brooklyn, New York in 1945. He joined a gang at age 14 and, three years later, was arrested for his first crime - possession of stolen property.