Personally,
If audible kill messages were enabled, I would ask for a way to turn them off. How does an audible message help? I have a similar position on night time (which I hate night, btw). I like to believe I am a WW2 fighter pilot while flying in AH2. Recorded voice kill messages and doing stupid things, like flying when you can't see, don't add to the experience. Hey, it's my $14.99.
Also, Betty's voice, while a pleasant tone, is a rude awakeing and not really desired. If I can't figure out a base is under attack, then an announcement to that effect doesn't really help (me). Having some voice telling me I just shot down a plane does nothing but add to the "Gamey" factor IMO.
Regards,
Malta