Serena got by No. 29 seed Kiki Bertens of the Netherlands 7-6 (5), 7-5 in the second round on Saturday in her return from a 14-month absence after giving birth to her first child. Venus preceded her younger sister on the stadium court and beat Sorana Cirstea of Romania 6-3, 6-4.
The sisters will resume their longtime rivalry on Monday. Serena leads Venus 17-11 all time and has won eight of their last nine meetings, most recently the Australian Open final last year.
It will be their earliest meeting since the sisters' first match in the series, a straight-sets victory by Venus in the second round of the 1998 Australian Open.
"Obviously I wish it was anybody else in the draw, literally anybody, but that's OK," Serena said. "Just have to go out there and see how I am and do my best."
Keys hasn't made it past the fourth round at Indian Wells in eight tries. The No. 15 seed was mistake-prone throughout the second-round match, committing five unforced errors in the tiebreaker.
Collins, ranked 116th and making her first appearance in the main draw, is just starting her second year on the WTA Tour.
She joined American upset winners Sachia Vickery, who beat No. 3 seed Garbine Muguruza; 16-year-old wild card Amanda Anisimova, who beat No. 23 seed Anastasia Pavlyuchenkova; and wild-card teenager Caroline Dolehide, a three-set winner over No. 30 Dominika Cibulkova on Friday.
In other matches Saturday, defending champion Elena Vesnina eliminated American CiCi Bellis 2-6, 6-1, 6-1; No. 4 seed Elina Svitolina beat Mona Barthel 6-4, 6-3; No. 12 Julia Goerges defeated Natalia Vikhlyantseva 6-4, 6-1; No. 27 Carla Suarez Navarro beat Su-Wei Hsieh 6-4, 2-6, 6-3; and No. 26 Daria Gavrilova dismissed Yanina Wickmayer 7-6 (3), 6-2.
Fifth-seeded Dominic Thiem fired 10 aces to beat Stefanos Tsitsipas of Greece 6-2, 3-6, 6-3; No. 7 Kevin Anderson defeated Evgeny Donskoy 7-5, 6-4; and No. 12 Tomas Berdych rolled past German Maximilian Marterer 6-1, 6-4 in just over an hour.