You need to find Bitching Betty's sound files in SS2's resources. They are inside snd.crf or snd2.crf (crf files are renamed zip archives). Once you know the name and place of a sound file that you want to override with your mod, you can rebuild that path inside DataTempMods.
To replace the sound where Betty says "Left" in the stereo test in the game's options screen, you would create this folder structure inside DataTempMods: snd\BBetty\english\left.wav
NewDark can use OGG compressed audio files too, as mentioned in the modders_notes.txt that you can find in the doc folder. This will make your mod much smaller.
When you're happy with the results you just compress the snd folder you created inside DataTempMods, give it a name like SS2_OneofTheMany_BitchingHEVSuit.7z and upload it to some file host. Then post the link here.