Hi
Sounds like you have been getting it right without our advice, its reassuring to come hear tho and get other opinions, isn't it?
As I said up to 30Min's independent play is about the max at this age, although it will vary from LO to LO. Maybe give her 15Min's in one environment then move her or change her toys for another 15Min's so she doesn't have chance to get bored.
Have you heard of the Treasure Basket as an activity, its a low sided basket and you fill it with everyday objects for them to explore on their own. I did one for my DD, in it I put clothes pegs, nail brush, silk scarf, lace hanky, length of ribbon, a walnut, wooden egg cup, wooden spoon, pastry brush, old mobile phone, cut out shapes of different colour leather, hair scrunches, golf ball, the list is endless really. I just went round the charity & cheap jack shops and picked up anything I thought would be safe and interesting to explore. DD loved her basket and would happily sit for 45Min's on blanket surrounded by cushions just exploring all these new things.
Hope this is helpful
newmum