Could be she is going through a growth spurt, there is one around 4 weeks, they can sleep more and feed more.
Also some babies do reverse cycle and sleep more in the day, so try and get her outside as much as possible, even if it is before a feed. While long term feed, activity, sleep is more ideal, it’s not going to do any damage to not do it in the early months.
Just keep trying to wake her after 3 max (esp if it is hot) hours and even give her a sponge bath if she is sleepy and even feed outside in the shade.
Hot weather can make them sleep longer too