Sometimes with mono there can be complications with the spleen which can enlarge and rupture or tear open. ZÕmm†dÐÁÎ!ƒ æactually in the upper part of the abdomen on the left hand side above the gastric area.  Could explain the pain after eating and having a full tummy etc?  It certainly sounds like the area you were talking about.  There can be pain, light headedness and a feeling like the heart is beating fast, possible trouble breathing and bleeding more easily. 

It's to be hoped that the ultrasound was accurate when they noted that it everything was fine.  I am not sure what they do if the spleen is affected, but it is obvious that it needs to be investigated and expecially if she has had mono.  Hope that everything works out ok for you.  It must be a worry for you all not knowing what the pain is.  

 

Take care

Val