OK, i figured her out. You need to gather 15 of the blue glowing orbs for energy to fill her flask, then, if you run out and reach zero hammer hits, you get to use that flask if you just wait about 3 seconds. I thought maybe there was an unlimited amount of hammer hits after that, but i was wrong, i was sown deep however in the necropolis so maybe if you were in the upper part you could dig more, but i did about 30 or so hits before she ran out of the flask energy from down deep, i think the first time i tried, i was up alot higher and i believe i got alot more hits. I guess the thinking is to go find more energy orbs before you run out again.

Try and use her as soon as you get her. If you got a small amount of hammer uses, this is better because the only way to get her flask is to get to zero on hammer uses, then wait a few seconds and she will get recharged. I died before she got a long way into it after i got recharged but it appeared there wasnt some set number of blocks you can destroy before it runs out, but that is a guess, as i died after i destroyed maybe 75 or so blocks after she recharged. As i got a lot of hammer uses, like 296 or so, it takes alot of block breaking before she can recharge again. So get her as soon as you can when you only got 100 or so, get it to zero, and get recharged and see how far you can go. also, i died, then got it to zero again, but didnt get recharged again and timered out, so not sure yet how to get recharged again, but im working on it.