Hey snowman! As a chick also, I luckily don't have that problem seeing I have size 9/10 feet, but there are two solutions to your problem:-
1. Wear boots - They make ur feet more wide, will grip into the footstraps, and your feet will stick in there quite well! (I wear boots just for protection agains the rocks etc., and they don't come out lol!)
2. Liquid Force sell heel loops for only $25, which slips over the back of your heel and is supposed to keep you foot in there! They just attatch in there quite easily!
www.liquidforce.com.au/ 3. or just push ur feet forwards a lot lol!
All the best mate! Let me know how it goes, and what helps you

Good winds!