According to api.tennis, Ostapenko and Mertens have met twice and have won one match each. In 2019, Ostapenko prevailed, and in 2020 Mertens leveled the series.
The 2019 meeting ended with Ostapenko winning 4:6, 6:2, 6:2. After dropping the opening set, Jelena took the next two by the same score and moved ahead in the head-to-head.
In 2020, Mertens won 7:6(5), 5:7, 1:0(8). This time Elise took the opening set, Jelena won the next one, and the decisive stretch brought victory for Mertens. That left their head-to-head record level.