she will need attractive (to her) nesting materials.  Some species of bombus
seek out old mouse nests in which to start their own nests.  This might be a
good start. You could experimentally add a few very young or emerging
honeybees.  It is possible that they might forage and thus enable the bombus
to expand her brood nest faster than if left to herself.
Today I saw some bumble bees seeking nest sites.  I might try this myself.
Chris Slade