Daughter is 6-7 weeks pregnant and had u/s today . No heartbeat heard. Is it too early to detect or not? She also had a pap smear two weeks ago and 2 days after started bleeding but has since stopped.

Fetal heartrate can normally be heard fairly clearly at 8-10 weeks. Depending on how much amniotic fluid you have. Which is also what determines how soon or strong you feel your baby moving. Doctors won't normally try a doppler until you are at least 8 weeks, since they most likely won't hear anything clear enough before that.
An ultrasound at 6 to 7 weeks is pretty early and is right at the first sign of pregnancy, so don't let that throw you off.

The bleeding after the pap smear probably had everything to do with her cervix and nothing with her uterus. The tools they use can irritate the inside lining of the cervix and cause minor spotting. If it went away after a few days and wasn't heavy, I wouldn't worry about it. If it returns bring her into emergency, especially if it is bright red.
But like I said, if it's gone, it was most likely just irritation, which happens to a lot of women.