Hi, T..
Do you breastfeed and bottlefeed? Or pump and bottlefeed exclusively? I'm wondering how your baby does at the breast. Has breastfeeding been "easy" or did you need help at first?
It sounds like maybe your baby doesn't seal well at the "corners" of her mouth, or the flow may be high. Have you tried the Dr. Browns *narrow* slow flow, or Ventaire *narrow* slow, or Nuby narrow slow? Sometimes wide (fatter) bottles prohibit a baby's mouth from sealing on the bottle.
As for flow, try offering the bottle where the milk is tipped below the hole, and after she starts sucking, tip the bottle up so milk flows. Tip it back down periodically so she can rest--this might lessen spilling.
I have co-authored a book that is currently in printing, Balancing Breast and Bottle: Reaching Your Breastfeeding Goals. We answer many questions like yours in our book. Our website will be up soon, too: breastandbottlefeeding.com.
You are welcome to email me privately if you have other questions.
A.