Mikayla approached Raj and flirted with him. Raj responded favorably until Leonard pointed out what her line of work was. Shortly thereafter, the two used their casino money winnings to pay her to entertain Howard, hoping to cheer him up after his recent break-up with Leslie Winkle. Mikayla offered to give their friend the "girlfriend experience" (which involved not revealing to Howard that she was a prostitute), to which Raj suggested making it the "Jewish girlfriend experience".
Howard quickly saw through the ruse, but was nonetheless grateful to his friends, particularly since she'd already been paid. ("The Vegas Renormalization")
Mikayla was portrayed by Jodi Lyn O'Keefe.