It was the season debut for 29-year-old McNeal and the first race in the distance in almost two years.
Since January, McNeal has been suspended pending the June 4 ruling.
The disciplinary body Athletics Integrity Unit, independent of the International Athletics Federation, sentenced McNeal to five years' suspension for manipulating doping tests, without specifying what it is about doping offenses.
The time of 12.50 makes her fifth in the world - after just one trial race.
World record holder Kendra Harrison was fastest with 12.49.
One month left until the Olympics
- I just want to cry right now.
You do not understand how much I have gone through that year, said McNeal, who was named Rollins when she won the World Cup and Olympics, according to the AP.
McNeal had to start the competition because she appealed the verdict to the arbitral tribunal Cas in Lausanne.
With the Olympics just over a month away, it is highly uncertain whether the court will have time to deal with her case.
McNeal keeps hope alive.
- I believe in my God and believe that I will have a fair trial.
That's the only thing I can hope for, said McNeal.