Witnesses said the woman entered the cafe at around 7:00 am before detonating her explosive vest in Bia, a village close to the border with Nigeria.
The area has seen frequent attacks by the Boko Haram jihadist group in recent years.
Those hurt in the blast were taken to a nearby hospital, witnesses said.
Since 2014, when Cameroon began its fight against Boko Haram, the group has killed at least 2,000 civilians and military personnel and kidnapped a thousand more in the country's far north, according to the International Crisis Group.