nrich is good.
For an able child, I'd steer her a million miles away from numeracy worksheets. That stuff is arithmetic, not maths. The purpose of the gifted and talented initiative (or whatever it's called now) is to engage and challenge the child - to make them think, in other words. Children who are drilled to be good at sums are sometimes hopeless at maths* - they fail to see the patterns or logic and have a poor grasp of how numbers work in the real world.
Good G&T activites will have a range of solutions and offer smart answers to random thinkers.
For example:
Give her an old cassette tape and ask her to work out how long the tape is.
She's allowed to take a metre out, but no more
Or a toilet roll, same rules. Or the groove on an LP.
Ask her how many blades of grass are on the front lawn or the number of grains of rice in a packet. Many children are at a loss to know where to start on a problem that isn't laid out as a series of instructions. Young girls often seem to need a "correct" answer to a maths problem - if she can accept estimates and explain reasonable accuracy then that is a massive leap forward from primary level numeracy
Look for number patterns everywhere - sunflowers, daisy petals. If she can express a pattern as (eg) 3n + 5 instead of "start on eight and go up in threes" she'll be streets ahead of the game.
Work on units too - she needs to know her weight and height in kg and cm. Be clear about the different units for length, area, mass and capacity. Prices and best buys in supermarkets give boundless questions - what's the cheapest way to fill a trolley at Tesco... that kind of thing.
I think it is much more about discussing and challenging her thinking rather than doing more classroom maths.
* Please don't think I dismiss the need to be good at tables and sums... but if your daughter has been identified as gifted, then just take those skills as a given. Don't bore her to tears by doing more workbooks.
Hope that helps?