if you are really worried then ask for something like emla (think thats the name) cream. It will numb the area and you wont feel a thing!.
I know how you feel, im needle phobic but getting over it slowly. As an example, rather than endure a little prick in my arm from a needle i gave birth without any pain relief!
most importantly tell the person taking your blood youre scared! They will do everything they can to keep you calm
I dont think anyone could be as bad as my hubby. He was in hospital, saw the needle & fainted. He asked the doctor why they didnt take the blood from him when he was outers & was told they cant. The doctor gave up as hubby trying as he kept fainting. I had to go with him to the ante room to hold his hand when he had to have an op.
Tell the nurse that you don't like needles and look away! It really isn't more than a scratch and doesn't take long to do. I'm sure that your mum could go in with you if you are really nervous. Good luck!