Tom,
Have them, or help them check out this list of Hummingbird Magnets.
It gives the corresponding growing zones for each plant from "A" to "Z". You may even be able to identify some of the reliable old standbys that others have talked about on the forums.

Good luck,
Lee

Here is a link that might be useful: Top Hummingbird Magnets

Tom
The link that Lee posted is excellent. One thing I will also add is that no northern hummingbird garden should be without these staples:
Coral Honeysuckle (Lonicera sempervirens)
Native Columbine (Aquilegia Canadensis)
Monarda 'Jacob's Cline' (Bee Balm)
Scarlet Sage (Salvia coccinea)

The first three are very hardy perennials up in the north and the scarlet sage is an annual but will bloom all summer long. Any of the Savia coccineas will work well. If you don't have room for anything else these will work wonders for your cousin.

Feel free to post the same question to our growing group of Michigan hummer gardeners

Penny

Last year I tried a number of hummingbird plants. Salvia Black and Blue and Agastache Tutti Frutti were the best attractants. Both bloomed early summer until frost. The hummers made short stops at the feeder, but obviously preferred these plants.