tendency 是源于动词 tend 的名词,tend 是不及物动词,常与小品词 to 搭配,表示“倾向于/有可能”.与动词同根的名词在用法上依然保持动词的用法特点,由此生成了如下的固定搭配：
have a tendency to do sth....有做某事的倾向/有可能做某事
因此本题应该改为 Vanessa had a tendencyher mind often,so often in fact that her friends gave up expecting her to show up at their parties.
另如：
* Paint has a tendency to bubble and peell over time.油漆因年久而开始起泡并脱落.
* Fabric has a tendency to wrinkle.布料可能会起皱.