Can start with rice cereal or purée then when she can sit without assistance can introduce more solid food or start BLW. My LO is 5.5m and opens her mouth when she sees the spoon or smell food so I introduced rice cereal and purée to her once a week. She still can’t sit unassisted so I don’t intend to start her on BLW yet.
But anyways, there’s no rush since babies below the age of 1, their primary food should still be milk :)