Well, Alucard can be killed ( happened in a recent chapter) but it took exploiting a loophole in the laws of physics to do so, and even then, there's a chance he'll come back.
But that's neither here not there,
if we're talking 100% both sides, then that means full moon, midnight, no holds bar. No corruption, no Roa, no restrictions.
Arcuied has her Marble Phantasm, allowing her to get away with pretty much anything that's physically possible.
Alucard is in full release,
To begin with, Alucard's army would be wiped out fairly quickly, even though he has a number of what's effectively Noble Phantasm's in his arsenal (Try and tell me Rip's Magic Bullet wouldn't be a NP in nasuverse), Marble Phantasm would make short work of them.
I'd say in terms of speed and power, they'd be more or less equal, and I'd say Alucard could survive a dose of Marble Phantasm ,
If we concede Alucard needs blood to regenerate, he's still got a good deal of blood to go through (several hundred yeras worth), and if Alucard doesn't recognise that he's running out of blood, then she may not simply spam MP till there's nothing left,
Considering Alucard's eye-shadow state of intangibility, I'd say if he was able to surround Arcueid and bite her, then it'd be his win, that is if he can get past her MP,
I think in the end it comes down to if Alucard gives her any free hits once she's serious(big mistake), and whether Alucard realises whether or not she's weakening him...
And yes, Shiki could kill Alucard. Provided he can get a hit in (Kinda hard to stab a moving shadow that's laughing at you)_