What's up with this new Mama cat? She had 6 kittens in a box in our basement this morning!?

The neighbor's pregnant cat adopted us when she decided she hated their new dog. She has had 3 litters (2 last summer, one the summer before). The neighbors say she usually "disappears" under someone's bed, and they don't realize she's had them until the kittens get noisy (they usually suspect she's had them somewhere because she's missing). So this morning, she had the 1st one and the last 4 in a box in our basement, and the 2nd one on our kitchen floor (which we promptly took to the box). She checks in with the babes frequently, but keeps coming upstairs and "hanging around". She has plenty of food & water, the kittens seem healthy, she's using the litter box. Does she just want attention? Should we move the box of kittens upstairs (the neighbors say she usually gets mad when you try to move her kittens). Should we be concerned that she isn't spending enough time with the kittens? The oldest kitten is only 11 hours old--what gives?