Is 18.1 megapixels a high quality camera?

I just got an 18.1 megapixel Nikon for my girlfriend for her birthday… It is the nicest one I could afford… Is this high quality, I know a few years back it would have been unreal, but I'm not so sure nowadays.

Megapixels mean how big the photo can be. It has nothing to do with quality. The quality of the camera depends of the lens, the aperture, the sensors, etc.

What kind of camera did you get her? Many cameras have 18 mp, some are good and some aren't.

There are many cameras with around 18 megapixels. Some are outstanding, others are good, some are not great and a few are garbage. On a small sensor, unless there's some processing voodoo going on, 18 megapixels is too much, like trying to put a racing car engine into a mini cooper. On APS-C or full frame, it's actually quite a good figure. But it is not even one of the important factors in terms of how good the camera is. The sensor, ISO performance and other things are more important.

The last time I used a Nikon, a couple of years back, it was a camera with 12 megapixels. It is one of the greatest DSLRs ever made and even now a used one will set you back three or four thousand dollars.

If your girlfriend knows what she's doing with a camera, she will be able to make good pictures with five megapixels, and if not, fifty megapixels won't help.

Megapixels are meaningless.

A top-of-the-line $6500 (body only, no lens) Nikon D4S is only 16 megapixels.

18 MP is only a good resolution for cameras that have a big enough sensor, i.e. A DSLR. Actually none of the Nikon DSLR's have 18 MP. Some Canon DSLR's do. The new Nikon DSLR's have 24 MP.
Getting back to yours, cramming 18 MP into a tiny sensor increases noise and smudgy noise reduction artifact. The camera manufacturers do it for the reason that your question implies. It is to attract buyers who think a higher number is better.
Most premium compacts, which use a sensor a little bit bigger than the cheapos, are aimed at buyers who know the difference, and so they hold the megapixels down to a more sensible 12 MP. Some premium compacts include the Nikon P340, Nikon P7800, Canon S120, and Canon G16.

Its the person behind the camera who makes the difference…
technically the pixels are okay but lot other things matter too…
don't worry she will do fine

It will take really good resolution images but, the main thing that makes a camera good quality is the colour it produces and the sharpness of the lens.

Yes! This is an amazing quality camera that will shoot impeccable photos/footage.
18.1 mps is awesome.

Do the waffles with huge squares taste better than the ones with tiny squares?

18 megapixels only tells us that the picture is huge. It has nothing to do with the quality of the camera or how nice the pictures will come out to be.