If you really want an espresso setup, you need an espresso machine and a good grinder (since you have to grind the coffee yourself to get a good cup). The basic Gaggia espresso machines are around 250, and they're pretty good for the price. A good grinder like the Gaggia MDF or the Rancilio Rocky will cost another 300-350 though. However I see some combo deals that are pretty good:
on this page, if you select the espresso machine + rocky grinder, it's just under 500$. That's roughly my setup.
But if you think your gf will be a bit lazy about this, then maybe you need a super-automatic machine (as opposed to a semi-automatic like the Gaggia I linked to above). Those are more expensive but they grind and brew automatically - you just drop the beans in. Not as fine-tunable but certainly easier to use. However they're more expensive, 500$ and above,
this would be a cheap one for instance. Used or refurbished machines would be cheaper of course.
If your gf doesn't necessarily want a "real" espresso machines, then a Nespresso machine would certainly work. They can make pretty dense coffee, but it's not as good as a real hand-pulled shot. Very practical though
. Those machines use Pods (containing ground coffee) instead of beans, which makes for easy disposal, although that means that the coffee will be a bit more expensive than if you buy the beans yourself.