There was controversy at Roland Garros when Thiem's post-match press conference was abruptly cut short in order to allow Williams to fulfil her media duties after her third-round loss.
It left Thiem, who was still in the tournament and made it to the final, seething and he later criticised the 23-time grand-slam champion.
"Mentally it was way more stress and pressure than I could have imagined," she said.
"I don't think there was anything that could have prepared me for that, especially since I'm kind of an overthinker.
"I think it's better for me now, I was going to say lower ranked, to be number two here because the only upside (of being number one) is if you win the tournament, you're automatically number one.
"That, for sure, is a really big goal of mine. I don't have to think about defending the ranking or anything."