Jamie, I don't know who that celebrity is, but her arms are very far from my definition of pretty...
smile_jma: As far as I know there's no reliable way to shrink that. You can avoid intense muscular effort where the veins are, but that's pretty much where it stops. Killing testosterone does have a very decent effect over time though. Unless I'm very hot or working very hard with my hands, my hand veins are almost invisible now, and they used to bother the heck out of me. My ankles though... they're full of brain-like, disgusting venis, as a result of more skin transparency. I just hide that. :p
Oh yeah, and HRT increases subcutaenous fat everywhere, while decreasing belly fat accummulations. If you're quite thin, once you've been on HRT for a while, gaining a bit of weight might help hide them.
Later, though, if you have a specific vein that doesn't go away and that really, really bothers you, maybe it can be removed at some medical aesthetics clinics. Basically they cause the vein to clog and die off, and the blood circulation just remakes itself around it. It's mostly done for unhealthy varicose veins, though, and I'm not sure if they'd do it for normal ones. But it's worth asking.