They did not expect to hear that the Cape Town native, who had just completed an internship at the city's Botanical Gardens, was planning to work with handicapped children.
"People thought, 'Why are you giving up your career and going to a foreign land - in the middle of a war - where you are not going to even be getting a salary?'" she said in an interview.
Others wondered why a South African looking to volunteer would travel all the way to Israel when there was plenty to do in her own country.
Despite the warnings, Isaacs pressed ahead.
"I wasn't afraid; God took my fear away," she said.
Isaacs first discovered her love for Israel when she met a group of elderly Evangelical Christians who were visiting the Botanical Gardens. They spoke about Israel "with a love and passion that I had never experienced," she said. "I realized that my steps were guided."
Isaacs, who was raised as an Evangelical Christian in an upper middle class family but who had not otherwise been especially interested in Israel, suddenly started going to meetings, praying for Israel and reading about goings on in the Holy Land. The young woman said she knew in her heart that this was only preparation for going.
Next, she spoke to her mother about Israel and its need for volunteers. Her mother, whose long-time interest in Israel had been revived by her daughter's sudden passion, said she would go first, and applied to be a volunteer.
"She had always wanted to go and serve Israel in some way, but was always concerned that she wouldn't be accepted," Isaacs said.
Isaacs's mother was accepted to work as a care-giver for handicapped children in Jerusalem in a program run by Ilan, the Israel Association for Physically Disabled Children. She urged Isaacs to come, but advised her to first learn a language.
"Actually, she said you have to speak Hebrew or Russian," Isaacs said. The young woman enrolled in a basic Hebrew course in Cape Town.
After her mother returned to South Africa, Isaacs set out for Israel.
For the next year, together with five Israeli teens performing national service and a non-Jewish volunteer from Germany, she worked with a group of 10 Israelis, aged 14-21, who have cerebral palsy.
Isaacs, who was repeatedly mistaken for a Jewish immigrant from Ethiopia, said most people were surprised to hear she was not Jewish.
In her halting Hebrew, she would repeatedly have to say, "Sorry, I am not Ethiopian, I am from South Africa."
Despite the wave of bombings that continued throughout her stay, Isaacs said her family was supportive.
"Megan, be strong. You will finish your term in Israel," her father would tell her.
After 14 months, Isaacs returned to Cape Town, feeling she had been strengthened by her service.
"It changed me, it made me stronger as a person," she said as she volunteered to help organize a pro-Israel conference, the "Jerusalem Summit Africa," that was sponsored by two Christian Evangelical organizations.
And perhaps not surprisingly, the avid lover of Israel has also been involved in marketing olive trees.