In March 2015, Charli XCX announced a collaboration with Sophie. It was later revealed that the pair had worked on multiple songs for her upcoming studio album. In September 2015, Sophie's debut album Product was made available for pre-order. The eight tracks listed were the four Numbers singles from 2013 and 2014, as well as four new tracks: "MSMSMSM", "Vyzee", "L.O.V.E.", and "Just Like We Never Said Goodbye". "MSMSMSM" was released on 29 September, and "Just Like We Never Said Goodbye" followed on 15 October.
In late 2016, Sophie acted as an additional producer on Charli XCX's song "After the Afterparty", which features vocals from Lil Yachty. The song is the first single from XCX's upcoming third studio album. Sophie cameos in the single's official music video. Sophie also received production credits for two songs on XCX's 2017 mixtape Number 1 Angel, and another for one song on XCX's second mixtape of 2017, Pop 2 which was released later that year.
In October 2017, Sophie made her solo musical comeback with a new single, "It's Okay to Cry", the first new material she released in almost two years. The music video for the song was the first time she used her voice and image in her work. She subsequently opened up to the press about being a transgender woman. Later in the month, she also made her debut live performance, where she premiered newly-recorded songs from her second album with vocal performances by Cecile Believe. One of the songs, "Ponyboy", premiered on Australian radio station Triple J, and the song was released with a self-directed music video on 7 December 2017. The third single from the album, "Faceshopping", was released on 16 February 2018 with a music video on 4 April 2018.
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