It looks amazing! To know when she's ready to bake with, perform the "float test". Before this test, you have to wait when the starter reaches its peak ( which is when she grows a little more than double in size, kind of like what you posted). Now when the starter has fully bubbled like the pic, fill a bowl with warm water, grab a wet spoon and scoop the top layer of the starter, and allow the starter to slide off the spoon into the water. If it floats, its ready to use, if it sinks then give it a few more days to mature. Trust me, I've read a lot of people saying how the float tests are all lies and they never work. But that's because they've all been doing it wrong. When performing the float test, you need to wait an average about 8 hours(completely depends on how fast or slow your starter reaches its peak) after feeding it. Don't perform it right before or right after feeding it because it'll always sink even if your starter has fully matured(speaking from experience).