hibiscus winter trimming
How does mother-in-law keep outside hibiscus for the winter?
Certified GKH Gardening Expert
Hardy hibiscus can usually survive winter outdoors in your areas, but in cooler regions (up to zone 5) will need additional protection, such as mulch and wrapping. As long as she can give it added protection during extreme freezing conditions (and as long as she doesn't have the tropical type, which needs to be inside over winter), it should be ok. The tropical varieties are the ones that require growth indoors over winter.
For additional information, this article may help: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/wintering-hibiscus-indoors-winter-care-for-hibiscus.htm