In other Fed Cup action this weekend, the Czech Republic beat Switzerland 3-1 and Germany beat Belarus 3-2.
Williams and Vandeweghe won their singles matches Saturday to give the US a 2-0 lead over the Netherlands in the best-of-5 event. Germany will host the Czech Republic in the other semifinal.
Williams will use the match as preparation for her full-fledged return to the WTA circuit at the March 5-18 BNP Paribas Open at Indian Wells before heading to Florida for the Miami Open.
"It's definitely the start of a long process, " Williams said.
"Physically I feel good and every day I get better and I get stronger, and that's just something I always keep telling myself every day".
Rinaldi did not rule out the chance of Williams playing singles on Sunday, saying only that adjustments to the current lineup, if any, would only be made after Saturday's action.
"Why not Fed Cup?" Karolina Pliskova, the Czech No. 1, missed the first-round match against the Swiss because of illness.
Cheered on by her younger sister Serena, who is poised to make her own comeback to the sport after a year away and the birth of her daughter, seven-time Grand Slam victor Venus made relatively light work of 124th-ranked Arantxa Rus, winning 6-1, 6-4.
Then, she came back to play the dead rubber with her sister Serena, in her first match since giving birth to her first child.
"Honestly, I don't really know about these milestones", she said.
In front of a roaring home crowd in mountainous Asheville, North Carolina, Venus won the toss and served first, closing out the opening game with a searing ace in an early show of intent.
"I was a bit nervous also because you (are playing) against such a great player", Rus said.
But Venus Williams, the fourth American woman to record 20 or more singles victories in the competition, saved a break point in the opening game and soon went 3-1 up.
They were level at 2-2 before Venus eventually began to pull away. Serving for the second time to stay in the set, Hogenkamp crashed as Venus went through the gears and broke to love, with some vigorous hitting.
"It's never a win until it's over", she said. It gave me an opportunity to be able to close it out for the USA. "I'm not really going for milestones, but then they happen".
'Actually, I think having a baby might help.
Serena makes her comeback five months after becoming a mother.
She is now one title short of matching Court's all-time record for Slam singles titles of 24 - a mark she is determined to better.
She added: "Right now I'm focused on this weekend and after that I'll figure out what it might be". "Sometimes that happens, (it's) just the beginning of the year".
Vandeweghe defeated Richel Hogenkamp 5-6, 7-6 (6), 6-3.
After holding serve in the second game of the match, Rus wouldn't win her serve again until she already had lost the first set and was down a break in the second. She teams up with Lauren Davis to face Lesley Kerkhove and Demi Schuurs of the Netherlands in Sunday's doubles match.