If my wife gives me money to help with mortgage, is this income?

We both own the house. The mortgage is ONLY in her name. I pay the mortgage from my bank account every month.

She transfers her money (usually half of the bill) to me via PayPal, and then I make one payment to our mortgage company.

Since she pays me in one transaction, and then I pay the mortgage, is her payment to me considered income? Or is this considered common cost sharing?

Thanks