Rachel, whose sister Margaret Kelly appealed for votes in last week's Times, was up against Sarah Lark after the pair received the lowest number of votes from the public.
The seven remaining contestants sang big band numbers on Saturday's live show, and Sarah's version of 'Mr Bojangles' and Rachel's 'For Once In My Life' were the least popular.
Rachel and Sarah performed 'As If We Never Said Goodbye', from 'Sunset Boulevard' on Sunday's results show.
Mr Lloyd Webber described Rachel as a "rock solid" performer.
"I'm really deeply concerned about you girls as I've been given a real googly again tonight. However, thinking about it long and hard I'm going to save Rachel," he said.
"I feel this is my fault because I told you (Sarah) to do "Mr Bojangles" in the way you did and I thought you did it wonderfully, however, I have to think as a producer and I do think Rachel was rock solid and there were moments that I did think that maybe you were a bit fragile. But you were wonderful and you did exactly what I asked and I feel dreadful."
Rachel's sister Margaret travelled over for the weekend show and admitted she was gutted to see her in the bottom two.
"She was disappointed with herself," said Margaret, who is from Mallusk. "We watched it back on the computer and she was able to point out to me where she was not at her best.
"But again, I want to urge people to pick up the phone and vote for Rachel," she added.