My Beautiful Laundrette

Omar Ali is a young man living in Battersea in the Wandsworth area of South London, right by the railway station[4] during the mid-1980s. His father, Hussein (known to the rest of the family as Papa), once a famous left-wing British Pakistani journalist in Bombay, lives in London but hates Britain's society and its international politics. His dissatisfaction with the world and a family tragedy have led him to sink into alcoholism, so that Omar has to be his carer. By contrast, Omar's paternal uncle Nasser is a successful entrepreneur and an active member of the London Pakistani community. Papa asks Nasser to give Omar a job and, after working for a brief time as a car washer in one of his uncle's garages, he is assigned the task of managing a run-down laundrette and turning it into a profitable business.
At Nasser's, Omar meets a few other members of the Pakistani community: Tania, Nasser's daughter and possibly a future bride; and Salim, who trafficks drugs and hires him to deliver them from the airport. While driving Salim and his wife home that night, the three of them get attacked by a group of right-wing extremist street punks. Their apparent leader turns out to be Johnny, Omar's childhood friend. Omar tries to reestablish their past friendship, offering Johnny a job and the opportunity to adopt a better life by working to fix up the laundrette with him. Johnny decides to help with the laundrette and they resume a romantic relationship that (it is implied) had been interrupted after school. Running out of money, Omar and Johnny sell one of Salim's drug deliveries to make cash for the laundrette's substantial renovation.
On the opening day of the laundrette, Omar confronts Johnny on his fascist past. Johnny, feeling guilty, tells him that though he cannot make it up to him, he is with him now. Nasser visits the laundrette with his mistress, Rachel. As they dance together in the laundrette, Omar and Johnny make love in the back room, narrowly escaping discovery. At the inauguration, Tania confronts Rachel about having an affair with her father. Rachel accuses Nasser of having invited Tania on purpose to have her insulted, and storms off despite his protests. Later that night, a drunk Omar proposes to Tania, who accepts on the condition that he raise money to get away. Soon after, Salim reveals to Omar that he is on to them, and demands his money back. Omar's father stops by late in the night and appeals to Johnny to persuade Omar to go to college because he is unhappy with his son running a laundrette.
Offering Salim a chance to invest in his businesses as a much needed 'clean outlet' for his money, Omar decides to take over two laundrettes owned by a friend of Nasser. Salim drives Johnny and Omar to view one of the properties, and he expresses his dislike of the British non-working punks in Johnny's gang. He attempts to run them over and injures one of them. Meanwhile, Rachel falls ill with a skin rash apparently caused by a ritual curse from Nasser's wife, and decides it is best for all that she and Nasser part ways. The next day Tania drops by the laundrette and tells Johnny she is leaving, asking him to come along. He refuses, implicitly revealing the truth about himself and Omar and she departs wordlessly. After Salim arrives and enters the laundrette, the punks, who had been lying in wait, trash his car. When he runs out on noticing them, he is ambushed and viciously attacked. Johnny decides to interrupt and defend him, despite their mutual dislike, and the punks turn their attention to him instead. As he refuses to fight back, they beat him savagely until Omar returns and intervenes, protecting Johnny as the punks trash the laundrette and flee the scene.
Nasser visits Papa, and the two discuss their respective failures, agreeing between them that only Omar's future matters now. Nasser sees Tania at the train platform while she is running away, and he shouts to her but she disappears. Meanwhile, at the laundrette, Omar nurses Johnny, and the two bond. The film ends with a scene of them shirtless, playfully splashing each other with water from a sink, implying that they are continuing their relationship together.

Question: Who was Nasser's mistress?
Answer: Rachel