DB Wiki says gohan taught her to sense ki after Kid Buu's defeat.
Ki control is pretty separate from sensing, including in earthlings. For Goku it was when he lost to King Piccolo and re-visited Korin. Could the young humans sense ki before visiting Kami and Mr Popo? Krillin didn't sense the danger from Raditz. Even Tien, who had flight - he didn't sense Goku's ki capable of killing Drum (ok, Tien was incapacitated) or sense Goku's power in the 22nd (ok, maybe he was too resentful or w'ever to acknowledge it) or even 23rd Budokai.