The best way to see whether your baby is feeding well is to check babies urine output,  generally they should pass urine minimum 6 times a day, the more the better. If it's less than 6 that means the milk intake is less. Coming to your baby as she is 1.5 month now, she requires feeding minimum 10-12 times a day on an average, slowly switch to on demand feeding as she grows little old.

You have to feed the baby every 2hours minimum, if the baby is demanding in between , then also you have to feed. You can feed the baby on how much the baby demands .