We spotted Tinashe -- looking insanely hot, BTW -- leaving Chateau Marmont Wednesday night and making her way to Warwick ... the same Hollywood club where Ben Simmons' rookie rival, Donovan Mitchell, was partying.

Our photog insists he saw Tinashe talking with Mitchell at Warwick ... but when we talked to the singer on the way out, she laughed at the insinuation she was shooting her shot.

In fact, Mitchell left the club a short time later -- with so many hot young ladies in his car he couldn't even fit 'em all in -- and made two chicks hit the pavement!

Meanwhile, Ben Simmons has apparently moved on to Kendall Jenner -- they went on a double date down the street with Devin Booker.