Hi Shelly,
I wouldn’t use Comfrey until after the bone has been set, as it’s a vulnerary and accelerates healing .
A comfrey poultice or salve can be applied topically, or a tincture of comfrey can be applied topically. Topical application won’t interfere with advil/motrin, or other medications taken internally.
Hope that your daughter-in-law’s pain has subsided, she’s had the bone set, and is healing well.