Yea well you could give her the money to contribute, it will have the same net effect, a lower tax liability for you as a couple.
But the contribution limit for her would be low, if earnings are low...i.e. if she is between 30 and 40 max contribution would be 20% of earnings.
Yes it would pass to her as part of your estate if you were to die before retirement.
If you died after retirement (you would probably take the AVC in form of Approved Retirement Fund - an ARF) she would be able to transfer it to an ARF in her own name with no tax on that transfer to her name.