@notthewhiterabbit
You sound like a really unpleasant person. Your poor niece, 
I hope she never gets to know how much you dislike her,. How horrible. 
As a few pps have said, you sound jealous and bitter, and resentful of your SIL.
@powaqa
I think you are getting a hard time here op. Not all families like let alone love each member. I wouldn't know my brothers children if I fell over them. I haven't seen them for 5 years and I certainly didn't love them then.
Wow, you sound as unpleasant as the OP. 'Yeah yeah, of COURSE it's OK to hate your niece!' 
@greatduckcookery
Not liking an older nephew or niece because of a certain trait or behaviour they display is more understandable than disliking a tiny baby only due to the fact you can't stand her mother.
This. ^
No-one is being 'dramatic' as a few posters are suggesting; it's just that many posters cannot fathom how someone can dislike a tiny baby because they hate her mother.
I personally would not let the OP near a baby or child of mine - not with the level of simmering resentment and loathing she clearly has for this tiny baby. (And the same goes for the few posters supporting her.) I hope the SIL and brother of the OP find out how she feels, and do exactly the same thing - (not let the child near her.)