The 23-year-old claimed Britain's one and only gold medal so far in Turkey in the 400m medley on the opening night and she is well placed to climb the podium again over half the distance.
With the heats making way to a straight final, Miley won hers in 2:08.86 to rank fourth overall 1.79 seconds behind European short course 200m medley champion Katinka Hosszu.
And Miley will be joined in the evening's final by British team-mate Sophie Allen with her time of 2:09.94 placing her just inside the top eight in seventh, 2.87 shy of Hungarian Hosszu.
Britain's women's 4x100m freestyle quartet of Fran Halsall, Rebecca Turner, Eleanor Faulkner and Lizzie Simmonds also reached the evening's final after ranking seventh overall in the heats.
That was it for straight finalists although former housemates Halsall and Simmonds and Georgia Davies and Jemma Lowe, a bronze medallist in the 200m butterfly, all advanced to semi-finals.
Davies and Simmonds led the way with the heats of the 50m backstroke first up on the penultimate morning in Istanbul, ranking sixth and eighth in 27.07 and 27.27 respectively.
Lowe then won her 100m butterfly heat in 57.53 for third overall while Halsall went one better in the 50m freestyle clocking 24.41 to place second behind fastest qualifier Aliaksandra Herasimenia.
Halsall was joined in the 50m freestyle heats by Turner but she was one of four Brits that failed to advance to semi-finals as, despite touching home in a personal best of 25.54, she was 31st.
Craig Benson was the best of those that did not advance in Turkey, missing out on a place in the 50m breaststroke semi-finals by just 0.07 after clocking a Scottish record of 27.28 for 18th overall.
Ieuan Lloyd set another Welsh record in the men's 100m freestyle, 49.09, but that placed him outside the top 16 in 36th while Matthew Johnson was 33rd in his first ever 100m medley swim.