The R.I.P singer looked unwell during the shoot, which was for Madonna's Material Girl campaign, and was then taken to her make-up trailer.
Shortly after, the pop star was seen being carried via stretcher to an ambulance, which rushed her to ER at Mount Sinai Medical Center in Miami Beach.
The 22-year-old was treated for heat exhaustion and dehydration, her doctor David Farcy told TMZ. She has since been discharged and is understood to be feeling better.
The incident took place on the beach near the SoHo Beach House hotel, where Rita later returned after a short stint in hospital, flashing a big smile to fans on her way inside.
Rita had been on Twitter just five hours before her ordeal to wish her brother a happy birthday. "Happy 16th Birthday to the best brother anybody can ask for! Don Ora I love YOU!!" she wrote.
She has stayed quiet on the Twittersphere front since the episode.
This isn't the first time Rita has paid a visit to hospital this year. In August she was forced to cancel concert dates when she was rushed to hospital with a throat and lung infection.
The blonde bombshell showed her dedication when she performed at V Festival on 17 August – just one day after she had been in hospital.