If you have got your own google account you can associate that with the market place (not Google Play). When you connect to the market place, you should be able to access settings the three dots top right of the screen and select Accounts, there you should be able to switch from your wife's account to your own google account. Though that may depend on your android version, mine was 4.0.4 and now 4.1.1.
Other than that I have no idea what you are talking about in regard to your wife's id and the avast mobile security as I can see no id branding on mine or any setting to set one.