Maybe a book series like Go Girl Angels would suit an 8 year old.

Ask her parents, they could guide you as to the kid of things that would delight her. Perhaps a book or jewellery, a purse with money inside. If she is the outdoors or sporty type perhaps something in those lines, if she is enjoys art, some art materials. She may enjoy spending special time with you, you might take her to a stage production or something or with your children,a trip to a zoo. Or you could take her out for a day, shopping and having lunch out would be so special.

Not sure where abouts you live but I am in the Brisbane area and here there is this lovely place at Springfield called ‘Little Miss Pretty Pamper Parties’ and you can actually do a package where you can get a mani or pedi and the little one will get her hair done, make up, pink lemonade in a champagne glass, age appropriate magazines to read, her nails done and a treat to take home. All of that costs $70 and there are cheaper packages available too. I am sure there may be other versions of this no matter where you live.
Other than that might I suggest craft activities- these are great because if she has everything already at least it is something that she can get creative with and it won’t really add to the clutter (this is coming from someone who has a daughter with too many clothes and toys!). Or another idea would be movie tickets- you could even make a day of it and take her out to the movies and somewhere age appropriate for lunch. Dreamcatchers are also all the rage too with young girls and make up is always good too.
Other than that my aunt had the great idea of taking my daughter out shopping and buying her what she wanted for her birthday that way so that she was able to have a day out and choose her own present. She loved that! And you can give a budget of how much you would like to spend.

Craft kits are a great idea because she had adapt whatever she is making to her own unique style. Gift cards are great too, it’s a fun experience to go shopping without mum or dad restricting what she can buy. Big w or Kmart have plenty of things to choose from and a $20 card would be more than adequate

A garden kit (grow fruit) or a big art set.

What about a nice jewellery box with carillon?

Tickets and a day out at the movies.
Loom bands or lego.
ice cream maker.
Accompany her to a concert or performance.
Take her and a friend bowling or ice skating.

kids that age love loom bands! or you can look in big w and d-i-y kid jewellery kits (bracelets and rings etc) are about $10-$15 each but are pretty fun

books
cake pop machine
clothes
gift voucher

Perhaps make up a little gift box, with some perfume, nail polish and some funky hair bands and clips in it.

Books are great. Gift vouchers are also handy and appreciated.

Some money in a card so she can get what she wants

Books, jewellery some kids makeup and also pretty things for their room

I don’t think you can go wrong with loom bands! Seems every kid around that age is into it right now, girls & boys both.

Other than that, books are great – at this age Roald Dahl is a favourite. And most parents love Roald Dahl too!

My daughter is turning 9 in June and loves Monster High Dolls. Also loves the craft kits you get from kmart in the stationary section. Loom bands are another great hit at the moment. Hope these ideas help

You might like to find out her favourite colour from her mum, and perhaps get a clothing item (scarf, jumper etc) in that colour.

I love books, judy bloom fudge series is amazing and perfect for kids her age

or even something from a movie she enjoys

loom bands if she doesn’t have any yet

Go to your library and ask what type of book 8 year olds are into. Be careful though, my daughter was a bit of a tomboy, so she was not at all interested in the ‘girlie books'”. I suggest a non fiction book with a few practical crafts in it.
(pasta for jewellery, making animals from paper plates, etc) This really gives her two presents – a book and crafts to do.

I’ve found that a voucher for an animal encounter at the Zoo isn’t that expensive and often the Zoo take a photo of the occasion. We did that for my nephew at Adelaide Zoo and he loved his Squirrel Monkey encounter