Seren Bundy-Davies set a personal best in the 400m at the Anniversary Games in London.
The 20-year-old Welsh athlete finished seventh in a race won by American Natasha Hastings in a time of 50.25 seconds with former Olympic champion Christine Ohurougu fourth.
Bundy-Davies' 51.48 was two-tenths of a second off her previous best.
"I'm really happy I came here and showed that I'm in PB shape. I'm really happy with that race," she said.
"It was amazing being alongside the likes of Christine, it was kind of surreal but I'm just really embracing it and enjoying it at the moment and I'm really happy I did that from lane one."
Earlier this month Bundy-Davies finished fourth in the individual 400m at the European Under-23 Championships in Tallinn, Estonia and helped the Great Britain and Northern Ireland team claim gold in the relay.