Need a Priscilla's dagger

Alright so after getting to Priscilla, I guess I overestimated her hp. She remaied invisible for me the entire fight, and I ended up accidently killing her. This is my first time playing through dark souls, and unfortunately I can see that I screwed myself out of getting Priscilla's dagger. But like I said, it's my first character and I wanted to make sure I'm not over looking anything, is there any way I can still get the dagger?
With the idea of online help on a side note though, if anybody has a Priscilla's dagger, is there anything you'd be willing to trade it for? (360, GT: Silver Reborn)
:joker:

I'll trade it +5 for any of the following

!.) A regular titanite slab

2.) A white titanite slab

3.) The crossbow Avelyn

No worries, if you're unable to trade for it, you can always try again during NG+.

On the note of still getting it, only via someone else. I don't see myself giving mine away, I am working on the achivement, nor do I really want to kill her again so I'm sorry I can't assist.

If you are unable to get one by trade my advice in NG+ is bring your strongest weapon, if possible buff it, and make your first attack on the tail. I don't really know if it takes more damage to make a tail weapon drop, in my opinion it would though but I personally don't know. I wish you luck, it's a fun dagger to fool with!

Alright, well thanks guys. I did consider the NG+ thing or else i'd be way more bummed out lol And The_Tao, I'll be sure to let you know if I come across any of that stuff, think I could have your GT?