Alright, mt94, here we go:
There are all different kinds of (home)-parties that make it harder or easier to be alone with someone. However, it is always possible to isolate one person. Ideally, you already know the next type of party and the venue so that you can already think about the whole concept.
At the party you can isolate her in two ways: Either by yourself or by using a wing:
-Yourself: First, I would concentrate on the other guests and "topics". Have a good chat with everyone, eat something, joke around etc. When you see her, don't ignore her. Be friendly, say hi, but keep on a normal level. As the night continues, you wil see her for sure. It will probably be in a group. So start an interaction with the group members and then I would begin to have a good chat with the girl *1* (see below). And then all you need is a justified reason to be alone with her so that it does not look too obvious what your after or how interested you are in her because that creates a lot of pressure on her (and on you as well).
You could do:
"Blablablabla. Oh, I need a new drink, come with me, because I don't want to interrupt the conversation right now".
"Blablablabla. Hey, your drink is empty. Let's get yourself another one."
Or, even better: You use a functional leave idea by relating to what she said. For example:
"Oh, really, you're interested in art? Then I've definitely got to show you that picture in X's room (or on the internet etc.)
Is it clear, how that works? From then on, it's the normal line:
Start breaking rapport, use some casual touches (reallly important!) and get smoothly more and more sexually. I would still recommend having some good conversation at that point, but you just need to control it. She could e.g. qualify herself, you could introduce more sexual topics etc.
It's just important to realize that she does not need any more comfort. That's why you really should focus on the touches, your voice body language etc.
*1*: Another great option would be to already use stealth touches already in the group. E.g. you could be talking to a guy next to her and moving your leg gently to the sound of the music. However, you're always touching her leg really really smoothly. If she keeps touching yours then it's on (there are more techniques on the internet). If you are going to use it then the situation is already more sexual at the beginning, so when you're alone, you've already got a lot done.
-Wing: This situation is perfect for a Wing. Tell a good friend BEFORE the party what your goals are and ask him for help. My plan is like that: He needs to isolate her and after some time you are "looking" for him for some reason. After you've talked with him about what you wanted, he leaves. How does it work?
Again, concentrate first on the other guests. Then, notice when he has got her (you can agree on a fix time, a sign (e.g. SMS) or just keep a "secret eye on him). After you've noticed his success, bump into him with a question that makes it logical for you to come by and ask him (it is probably best to relate it to a common event in the recent past). Then you say hi to girl, he answers the question, you're chatting aroung for a short time and then he should leave. Now that needs some thinking: He could leave on his own but that seems a bit obvious to me (although there a ways to make it reasonable). The better way is probably for you to bring another person into the conversation. Your wing ist going to have conversation with that person, mangages to away with this individuum and there you are

Note: Your company, that your first wing is going to take care of, could even be a second wing of yours.
Alright, did that help you?