Are you referring to bags under the eye or lacrimal sac swellings.
Eye bags are due to loss of elasticity and laxity of eyelid tissues. Since there is lot of loose tissue so fluid might accumulate there. Get your mothers kidney
function done . Other thing is allergic angiooedema of the eyes when redness
and swelling occurs after the allergic reaction
to something and crusting may occur in such cases.
Get her checked by an oculoplastic surgeon or you may show us the photographs if that is possible somehow.