Andrew looked shocked by the news, while Caroline quipped: "Good job I haven't unpacked my case yet."
Viewers will choose between her and marketing manager Andrew to be thrown out of the house where a group of people are living together without contact with the outside world for Channel 4's interactive TV experiment.
Last week, Caroline was nominated by her housemates for eviction, but writer Sada was given the boot by viewers in a telephone poll which closed on Friday.
Andrew looked shocked by the news, while Caroline quipped: "Good job I haven't unpacked my case yet."
The results of the phone vote will be revealed on Friday evening.
Bookmakers Ladbrokes have made Andrew 8/11 favourite to be evicted, with Caroline on even odds.
Last week's nominations were split on gender lines, with the five men voting as one to throw out Sada and Caroline and the five women mostly voting to evict two of the men.
But this time the men broke ranks, with Millennium Dome worker Darren backing Anna, Caroline and Nichola in voting to throw out Andrew.
Caroline was selected for eviction by Andrew, Craig, Mel, Nicholas and Thomas.
Craig, a builder from Liverpool, proved unpopular with Mel, Nichola and Nicholas.
He frustrated some house members by injuring his leg while taking part in the housemates' latest challenge - to ride an exercise bike for the equivalent of 1,800 kilometres.
Only Anna and Nicholas received no nominations - despite the fact that TV viewers have seen Nicholas conspiring to see his fellow contestants removed.
Andrew, 23, made an early impact on the contestants - and the tabloid press - when he revealed he had taken part in a live sex show in the Philippines.
Caroline, 37, now works as a telephonist but her earlier careers involved selling sex aids for Ann Summers.
She was spared by viewers last week, but was seen by viewers on Monday evening opting not to unpack her suitcase - just in case her luck failed to hold out.
Ten contestants entered the Big Brother house in Bow, east London, on 14 July.
They are not allowed access to the outside world, and are watched by scores of TV cameras, picking up their every move.
Provisions must be bought from a tight budget, and they can let off steam in a special "diary room".
Each week, the contestants nominate two of their number to be evicted, with viewers voting for the one who will be thrown out.
The one who remains at the end of the series wins £70,000.