Agony: she says 'I am not up to the task'

My girlfriend says ‘I am not up to the task'

 I have been in this relationship for a period of about a year. I love her so much. She is beautiful. I however, do not like it when she compares me to her ex-boyfriend. She boldly told me that "I am not up to the task in bed."  She went on to say that his ex-boyfriend was pleasurable. What should I do?