Looks like we've got a late bloomer!

Today I took Abbie in to the doctor for her 12 month well child check.  Let me just start off by saying her old NP left to work in Chicago.  That makes us very sad.  We really loved her.  So now we must see a new NP who has never seen Abbie before.  She was VERY concerned with Abbie's size.  So here I am in the pediatricians office feeling like a horrible mother, trying to explain that she is just small.  I felt like I had to justify myself to her so she didn't turn me into CPS.  I was very nervous about this visit because I knew that Abbie's old NP was gone and that I was going to have to see someone new.  So after she asked me a numerous amount of questions she informed me that Abbie must go for blood tests to check for multiple diseases to explain her size.  She weighed 16 pounds, which is below the 3rd percentile.  She also let me know that based on the test results she may want a GI consult.  I was of course annoyed about it, but I kept my feelings to myself.  After Leaving the office I informed Len of the situation, which was obviously a bad idea.  Of course a fourth year medical student is not going to agree with the NP's orders.  So here I am trying to figure out what I should do.  My mother instincts tell me that nothing is wrong with her and I don't want her to have to go through anything painful, but my Nursing instincts tell me I should have the test done and let the results speak for themselves.  What is a girl to do?