Vitamin D Drops

My baby girl's pediatrician recommended for me to start supplementing my breast milk with vitamin D drops. My husband's aunt actually gave us some as a baby shower gift, along with other must-have items (that are often forgotten) that she put inside a basket for us. The brand she gave us is Mommy Bliss. They are organic vitamin d drops. Any experience with this brand? I nurse her majority of the time, she only has about two bottles per day (sometimes not even that) so we haven't given her the drops yet. I just want to know which brand is best before we start giving it to her. Also, is it okay to just give her the drops in her mouth?