Most pediatricians recommend waiting until 6 months, though some give the green light at 5 and a half months if your baby is already showing the right signs. It's not as rigid as it sounds - it really depends more on developmental milestones than on exact age.
The real signs are these: your daughter needs to be able to sit up with minimal support (not completely on her own, but almost), she needs to have lost the extrusion reflex (meaning she's not automatically pushing everything out of her mouth with her tongue anymore), and most importantly she should show interest when she sees you eating - like following food with her eyes, trying to grab it, putting her hands in her mouth. If she's already doing these things at 5 and a half months, you can start without worry. But if she's not there yet, it's better to wait a few more weeks even if she's almost 6 months.
Honestly, the difference between starting at 5 and a half months and 6 months is minimal. What matters is that your daughter is developmentally ready from a neurological and motor perspective, not the exact number. And most importantly: if you have doubts, your pediatrician knows your daughter better than anyone else, so listen to what they tell you rather than going by what people say.