@raynbow- It definitely sounds like your friend had an allergic reaction to eating shrimp. Though it can take several hours to occur, an allergic reaction to foods like shrimp typically take place fairly quickly after eating it. On the other hand, the symptoms of food poisoning may take hours or even days to emerge.
To be sure, your friend should talk to her doctor before eating shrimp or other types of shellfish again. Though it sounds like her reaction was somewhat mild, if she truly is allergic to shrimp and shellfish, she could have a more severe reaction the next time she eats it.
There are certain types of allergy testing that a medical professional can do to see if someone is allergic to specific types of food. These tests would save your friend another uncomfortable allergic reaction in the future once she finds out what foods she truly is allergic to.