Did you (or your sister) know that brain cells in babies' brains only form connections when a baby is held?
Consider how the other primates (we're primates, that's our animal category) raise their infants - they don't put them down at all in the first year, some for several years, except when the baby wants down.
The reason is undoubtedly related to brain development. Before 8 months old, human babies are still 'fetal' = they have to come out at 9 months gestation, or they won't fit out, but they are not ready to be left alone when born. They need to be held all day. They need their mommy's milk on demand.
Your sister is totally wrong - meeting your child's needs is the way to make her strong and independent. A child who is rejected (how a baby perceives not being held when the baby needs holding) may put on the facade the adults want - a phony independence - but what you get is a depressed, withdrawn, or angry kid.
Hold your baby as much as she asks and you will be rewarded with a happy, independent child who TRUSTS YOU and wants to please you.
Plus, remember, the brain cell connections. Put your baby down and you are literally lowering her I.Q.
Get a sling - baby's too small now for most models, but soon she's love a sling and you'll have more ability to move around.