baby spitting out lil feed during burping would be normal as it comes out while the air in the tummy is trying to escape. or in some cases baby spits out the feed that was in excess for him/her.
Next Steps
u can burp the baby before giving her formula feed, after the breast feeding.
Health Tips
if the babys weight is growing well for her age and she is getting enough milk with just breastfeed, u need not give formula.