Try using a lamb nipple instead of the big calf one.
I've found that especially with small calves that sometimes those big calf nipples can deter them.
Keep trying.
Does the calf have a suck reflex when you gently wiggle your finger in her mouth?
Is she otherwise vigorous?
Are you trying her with the bottle when she's standing?
Also, if you've had to tube feed her, give her a good four or five hours to become hungry before you try bottling her. You'll know she's getting hungry because if nothing else her muzzle will start to become wet with saliva...also usually hungry calves become restless and start moving around more than full ones.
And yeah, it's gross, but rubbing them around their rectum will stimulate the suck reflex (it will also stimulate other messy bodily functions, so be prepared). ;-)
Take care and good luck with your calf.