my daughter's freaking me out...

so I recently found out we are having baby number 2! I'm 6 weeks 2 days. for the last week or so my daughter (Who had no idea) has been poking my belly saying my baby sister is in there. Its early and I am slim and only had a little bloat so it's not like I have a bump already. she's literally said it every day for the last week. I keep telling her it a food or that my belly is full of cake or whatever but she says "no mummy it's a baby..." . I want to tell her but I'm scared it's so early. I had a scan last week as they thought I was having an eptopic pregnancy and thankfully it was all okay and was just a burst cyst on my ovary. when they scanned they said everything looked perfect for how far along I was. I just don't know if I can keep lying anymore as she is adamant. would it be wrong to tell her so early or should I wait? advice please...