Depends on how well she can sit and what type of high chair you have. I have one that reclines and can effectively be used from when they are tiny. I have been using mine for my children from when they were 3/4 months. If it doesn't recline or is not padded/has no support she needs to be able to support herself really. Look at the guidelines on the instruction booklet for your high chair that should help

Hi Lara - I invested in one of those Stokke chairs which is much more like a piece of furniture and grows with the child. It cost me £150 but my daughter was able to be safely strapped into it from around weaning time - 5 months and I've only just lent it to a friend. My daughter is now 6. Ikea do something similar and I think the high end people do - like mamas & papas. Often the cheaper ones not only take up a lot of space but once the child wants to sit at the table with the family - you've got to buy another booster chair so it can end up false economy - let us know how you get on! Good luck

I used a HandySitt when Thomas was 7 months old. The minui HandySitt can be used from 6 months (or when your baby can sit up unaided) up to 5 years. It's brilliant because it straps on to any chair, so I can take it with me when I go to my Mum's. You can also get a padded cushion for it so your daughter won't slide about in it if she's very small.