As a pediatric physical therapist, let me reassure you that all children develop at their own rate. 6 months is the age and stage where children begin to sit up and support themselves, not necessarily when they accomplish it 100%. I would recommend a regular visit with your pediatrician just to be sure he/she doesn't see any underlying issues. Then there are lots of fun, play things you can do with your little one to encourage her to sit up and to develop her trunk (abdominal, side and back) muscles to help her attain that goal. You can play a "sit up" game where you lie your daughter on her back on your thighs while you are seated comfortably. Hold both her wrists (not hands as this can put undo stress on the little wrist) and gently pull her into a sitting position, encouraging her to lift her head first then help you more and more as you play. Once she gets into the sitting position, blow a raspberry, give her a kiss on the nose, anything that she finds fun and entertaining (believe it or not, laughter in babies is a very effective way to strengthen muscles) because it will make her want to do it again and again. You can also sit on the floor with her surrounded by lots of toys. Put her in a seated position and then support her only at the hips so she doesn't totally tip over. Then have your hubby engage her to reach and grasp objects so that she has to lean to the side and the front and sit herself back up. Above all, play with your baby. This isn't meant to be stressful for either of you. It should be fun and entertaining, that's what makes it work. Unless your pediatrician finds some underlying issue (which is doubtful) you should see progress steadily but not necessarily overnight. Be patient. Kids develop at their own rates. The guides that give ages where things should be accomplished, are just that, guides. Have fun with her!