Pregnancy question

Ca

My little sister asked me a question I could not answer..maybe y'all can. She said she had sex on her ovulation day and they didn't use protection. They been trying for a couple years. Anyways, she said that she's been feeling nausea and just weird today. Her ovulation day was 2 days ago. She wanted to know if it was possible for her to feel like that? If that makes sense. Thanks