The Nikon DSLRs will accept older Nikkors, with certain exceptions. There are tables online that will give you compatability.
I have a Nikon D1x and it will accept all my manual focus Nikkors except those that are non-AI. It will operate in aperture priority with those lenses, but not matrix metering.
I had a Nikon D70 that would accept manual focus Nikkors, again, not those that were not AI (automatic indexing, introduced in the early 1970s), but would not provide metering with those lenses.
If your wife wants to use her older lenses, her best bet would be to buy a used Nikon D1X or D2H, both of which can be found for under $600 at
www.keh.com in varying condition. That would give her full, or nearly full, compatability. The fisheye may not work if it is the older model that required the mirror to be locked up when installing the lens.
I love my D1X as I have a large collection of manual focus lenses that, to my mind, are alot tougher than what's on the market today. I also think autofocus is unnecessary for anything but highspeed photography of moving objects.