I would go for a bigger wheel now. Although she can run ok in the 8" now, they run much better in a bigger wheel anyway. The 11" (28cm) Trixie wheel is popular and one of the cheapest. If you like the Karlie wood wheel you have now then get the 29cm one. I had the 29cm one for a while and really liked it. Unfortunately ours broke and I got fed up waiting for replacements when one arrived damaged, so got something else.
As the others say, if you get the 29cm wood wheel, it might need some light sanding and then painting with plastikote. There have been some issues with splinters. That's not as bad as it sounds (sanding). I'd never done it before and it only took 10 minutes. I bought some sheets of sandpaper at the local hardware store and found the 240 grade and the 100 grade were the ones to use. One is rough and sands the struts to get rid of splinters (and any other splintery parts). The other one is very fine and finishes it off nice and smooth
The plastikote also helps seal it as well as waterproof it.
They are lovely wheels and quite and our Syrian really enjoyed running in his 29cm one then jumping out and flopping on a big pile of substrate. He also loves his current wheel as it spins so well.
I wouldn't use a flying saucer as a main wheel for a Syrian - they don't always run straight on them - it can be nice as an extra toy in a cage if you have a standard wheel as well, but they need to be 12" for a Syrian and take up a lot of space.