Wow! I wish my dd had been interested in sewing!
The one I have seen recommended is the Hello Kitty by Janome. It's not a toy sewing machine, but rather a 3/4-size sewing machine. I think it would be perfect for interested 8yos! Here is a link to it:
http://www.american-sewing.com/janom...-3-4-size.html
There are other Hello Kitty machines; your friend needs to be sure it is the version made by Janome. The others are just toys.
An alternative to the Hello Kitty by Janome is one of the Janome Jem machines. These are also 3/4-size machines but made for serious sewers. It's an entire line, with the more expensive machines in the line having more features. Here is a link to one of the machines in the line:
http://www.sewvacdirect.com/janome660jem.html
These may not be the lowest prices you can find; I just did a quick Google for them. I think your friend will find that the reviews on these machines are very positive.