Hi,
To be honest, just in these early days, and until you are sure she is on track and gaining weight I would tend to wake her and feed her every 3 hours (if she wants more feeds than that, that's OK - but don't let her go more than 3 hours) For most people, babies included, 6 *feeds* in 24 hours wouldn't be enough to grow on (think of every time we put food or drink in our mouth). There can be a number of reasons newborns don't feed enough, and they haven't got too many reserves of energy to fall back on. The general rule of thumb is that babies lose around 10% of their birthweight and you would usually expect them to be back at birthweight by 2 weeks. The key to imput is often output. What are her wet and dirty nappies like? By this age she should be having several poos a day - and they should have transitioned through black meconium/green/brown to mustardy yellow.
Pretty soon you'll be able to let her do her own thing