Aspen Fleabane (Erigeron speciosus)

Aspen Fleabane, also known as Garden Fleabane, Showy Daisy, Fleabane

It sounds like you're describing Aspen Fleabane, a clump-forming perennial belonging to the daisy family. This plant features pink, white, or lavender blooms and is native to parts of North America. It thrives from summer through fall and is often used in gardens for ground cover and borders because of its showy flowers.