They have to run in the bigger races to get the rating. The key is seeing that they look capable of more.
Chase ratings are also usually a few pounds higher, not sure why but always have been.
Annie Power was rated 162 when she won the Ch hurdle. She had randomly been raised to 165 prior to her stayers run after winning a couple of grade 2's.
Honeysuckle was rate 161 when she won her first, so got rated higher (165) after that, and no higher.
Epatante was rated 159, and was given 162 after winning her champion hurdle.
Don't need to speak about Golden Ace
So going in with a 160 and getting 7 on top is a tough ask for any opposing horse really, and IMO she'a probably worth another 3 or 4 on top.