You can hit her with knives but I didn't have enough to finish her off.  She was also kinda spamming her beam attack at me since I was consistently out of her melee range.  You might be able to make it work if you had the cannon ready, but I couldn't do enough ranged damage to make it happen.  

The One Reborn is one of the easiest bosses in the game. You shouldn't need any glitches to beat him, or any other boss for the matter. Especially on your first play through.

There's a good way to farm blood echoes in Mergo's Loft: Middle. Just run past the 2 big pigs and you'll eventually stumble on 4 shadows of yharnam... if you run past them, there's a 90% chance of the pigs hitting them and everyone will start fighthing against each other. Usually when they're done fighting against each other, there's only 1 or 2 weakened shadows left, the pigs are dead and you've earned tons of echoes by doing nothing in less than a minute. xD Then you could just backtrack everything and face the weaken, or single, enemies on the road to gain even more echoes.

Yes i farmed there a lot, too. But i killed them. Alone the first pig gives 10k. In the end, 1 run up to the boss is worth 1 level (more or less, dont nail me on exact numbers, please). But yes, its easy to farm there.

if you want to farm echoes just go to a depth 3 or higher dungeon with moon runes and just watch th echoes come in. was getting over 100,000 souls in like 10 min

if you put on the 3 echo runes, you ran get 21k every minute on the first floor lecture hall. just kill all the blobs in the auditorium, then use a hunters mark to reset. they are slow, weak, die fast and the area is separate from the rest of Yarhnam so Itll load faster than any other area and its right next to the lamp. r2 attack gives slightly more echoes then r1.

45 seconds ish to clear the room, including the 5 seconds it takes to get there from the lamp. load screen is like 15-20 seconds. and because its so easy, you dont need to worry about dieing

im pretty sure they stack, cause i can remember doing the run with different rune sets and getting anywhere from 9k up to 22k per run.  its nice cause once you get the rooms attention you can stand in the door way and just swing, they all come to you,  then you restart.  its braindead simple and hard to mess up lol 

and ya its good for up until youve got to depth 4 or so.  when i was doing them i would end up with a few hundred k every so often and was surprised how much i got,  but you do gotta be careful when you get to that point  cause some of the minibosses can 1 hit you if your not paying attention lol