The Lady Black Cats beat Reading 3-0 to make the semi-finals with Arsenal, Manchester City and holders Chelsea.
"If you want to win a trophy you've got to beat the best," Williams told BBC Newcastle ahead of Tuesday's draw.
"Whoever we get, we'll prepare appropriately. We're not going down without a fight."
Carlton Fairweather's side had drawn 1-1 with Reading in Women's Super League One on 26 March.
Ex-Doncaster defender Williams continued: "We played Reading in the league last week and we felt that we underperformed quite badly.
"So we had a chat first thing on Monday morning, we had a look through the videos, discussed what we needed to improve on and we applied that."
Sunderland Ladies have only played in an FA Cup final once, losing 2-1 to Arsenal in 2009.
"It would be massive if we get there [the final]," the 25-year old added. "It's every kid's dream, isn't it? You don't get many chances to play at Wembley and you've got to work hard to get there."

Matthew Daley, 34, of Worthing, is being held on suspicion of murdering Don Lock, 79,  and police have until midnight to charge or release him.
Mr Lock died from stab wounds after a suspected road-rage confrontation near Findon, which Sussex Police described as an "unprovoked attack".
On Saturday a knife was recovered and sent for tests.
His family gave an emotional news conference on the same day to pay tribute to the man they described as "gentle, kind and loving".
Mr Lock's son, Andrew, said the family had been "incredibly overwhelmed" by messages of support and they were "deeply grateful" to the people who had tried to treat Mr Lock at the side of the road.
The great-grandfather had recently celebrated his 55th wedding anniversary with his wife  Maureen and had also been given the all-clear from cancer.
He was attacked after getting out of his car following a crash with another vehicle on the A24 on Thursday evening.
Paramedics were called but he died at the scene.
On Saturday Det Ch Insp Paul Rymarz said Mr Lock was the victim of a "violent, unprovoked attack that he had no chance to defend himself against".
He described the investigation as a "fast moving operation" and renewed his appeal for anyone with further information to contact the police.
Defender Victoria Williams says Sunderland Ladies will "not go down without a fight" after reaching the last four of the Women's FA Cup.
[NEXT_CONCEPT]
Detectives are continuing to question a man about a fatal stabbing after a car crash in West Sussex.