Thanks for writing in to Heathcare Magic!
Lasilactone is not known to cause mouth ulcers.
It can cause dehydration
but hardly ulcers.
May be your mother is having congestive heart failure
, your doctor knows her better.
Do not change/stop any treatment without the knowlege of your physician.
The swelling can be induced by certain drugs also.
What medicines she is on currently?
If you have any further query please let me know I would try to answer it for you.
Wish you a great health!