Hell no I wouldn't let my gf do that. The only thing she can stick in my ass is her tongue.
As soon as that strapon goes between the cheeks, you become the bitch in the relationship. If being submissive is your thing then go ahead.
http://bp2.blogger.com/_fznb4r2XX6o/RZVfUrQ5oPI/AAAAAAAAAuw/O44ZrNjPhVQ/s1600-h/Big-Tit-Porn-V2317-a_07.jpg
It looks like Cassandra but she isnt that skinny, is she?