First, you need to watch her. Most of the time, a Succubus' drain is very pleasurable. There's a good risk of addiction. Theoretically, blocking their memory of the event is a reliable safe method, leaving them just abnormally and, far as they know, inexplicably attracted to you - with the kind of person relevant to you, that'd probably be more than enough to get control of the situation. If you're unwilling to do that, then you have to hope that the subject doesn't, basically, fall in obsessive love - it can take quite a bit to break that, even with magic.

The bigger worry, however, is you. In two ways. While physically the energy's the important part, most Succubi have a strong dominant streak. Quite simply, if you drained her and KO'd whoever it is - who is it, anyway? - your physical need is met, but the mental want isn't. The result could make it even harder to control your desires.

Of course, there's the amoral solution to both issues, but...