It looks your mother has developed chronic UTI and in such type of chronic infections,you need to give proper antibiotics,after culture and sensitivity of urine,for many months.
There are several conditions which make the urine tract infection chronic and these are
Lying immobile for a long time
if you have chills
or back or side pain,then this could mean kidney infection
You have to get all the investigations done to see for any problem which might be making it difficult to treat UTI.
these investigations are
You must consult a urologist
and take proper treatment after all relevant investigations.
She shall definitely be all right.