Big Brother evictees Katie and Lucy Mercer hope their "sugar sisters" tag sticks with them outside the house.

The Perth siblings spent 66 days in the house playing as "one" contestant under the rule they had to stay within three metres of each other.

Now they're free to roam wherever they want after they became the 10th contestant to be evicted after the hasty departure earlier this week of three-day intruder Justynn Harcourt.

The sisters were evicted after receiving the fewest votes to be saved on Wednesday night's live show on the Nine Network.

"We absolutely love the name sugar sisters," Katie told AAP on Thursday.

"We both have sweet teeth so it definitely suits us."

She said they had a distinct advantage over the other housemates because they could emotionally support and confide in each other without putting anyone offside.

Also having to be within three metres of each other, it meant they were usually involved in the same conversations and none of the housemates could conspire to cause them to fight.

"It definitely helped that we had the support of each other in there," she said.

"The fact we are so close and loved being no more than three metres apart made our relationship even stronger.

"It was so much fun being together the whole time."

Katie, who works in the emergency department of a Perth hospital, was unclear about whether she would rush back to the west and start work again.

She also said Lucy, who has only six months left to complete her bachelor of education degree, was in a similar predicament.

"I absolutely love being a nurse but we are open to what happens and we are going with the flow," Katie said.

Upon their exit on Wednesday night, housemate Mikkayla started sobbing uncontrollably and Katie said there are likely to be a lot of tears spilled by the time the winner is announced.

She was tipping Ben to win the series but also said it was possible for one of the three intruders to pull off a surprise victory.

"We definitely think Ben will win, he is such a genuine person and he is so funny and does not even know how funny he is," she said.