Watson crashed out at Roland Garros on Thursday by going down 6-2 6-4 to the Romanian, and appeared to slam her racquet to the ground in frustration.
"Simona played very well, as I knew she would," she told reporters. "I don't think I was on my best game. I made a lot more unforced errors than I usually do, and I thought my first-serve percentage wasn't very high.
"But she made hardly any unforced errors. She made me make those unforced errors. I've got to give her credit for that. I felt she was a bit nervous in that last game. So was I, and I didn't take advantage.
"I'm disappointed that I didn't do better. I really expected more from myself. It happens, and I'll just take these weeks as a positive for the grass."
Despite the defeat, the 22-year-old will leapfrog fellow Brit Laura Robson in the WTP rankings.