There are some good points to mention in your shot, such as the expression you caught, the catchlights in her eyes (which look like you were using flash, which if you did is nicely balanced and has given an even light without harsh shadows). So it's not a bad start at all if you ask me.
Highchairs are handy (I have a 17 month old) as you can keep them relatively still. If you can, as already said, get the window behind you even if you need to move the table, spin the chair round until the light looks right (with some shadows to provide contours to her face) and try again. Depending on the light you may not need flash.
Some additional pointers to try, use single point focus and focus on the closest eye, take loads of shots as it's hard to wait for the right expression and it's easy to miss and do something to make them laugh (whatever works for your daughter, with my son last week I was banging myself on the head with the case from the flash and it made him giggle every time I did it, long enough to get some lovely smiles). You haven't got her dead centre in the shot which is a good thing (though opinions differ and sometimes central works) but she is a little close to the edge of the frame. And as already mentioned... background, keep it plain to keep the focus on the subject, whether that's a plain wall near good light, a blanket over a sofa, I'm sure you get the idea. Shots of them playing also work, especially if they are concentrating on something enough to keep them relatively still. Gives more context to the shot, which 'portraits' don't.