Ok so this is nothing complicated and I have ideas on what to do already but I'm curious to get another person's perspective on this dilemma.

I have been very flirty with this one particular girl, the only reason I've been hesitant on making a move on her is because she is my friend's sister. He's cool with me talking to her, the only thing is that we're always hanging in a group with our other friends(4 other people) and I'm never really alone with her. I've done nothing more than cuddle with her. I think she maybe attracted to me because she is always touching me and smiling, and she's comfortable with me touching her, even her face! I've been trying to make a move on her for the past 3 weeks(we've hung out like 5 times)and the last two times I saw her(friday and Saturday) were kinda lame. I was thinking of giving it one more shot and if it doesn't work I'm moving on. I want to set up a time to hangout with her one on one, but I don't want to be direct with her. I kinda play it somewhat conspicuous with her so it wouldn't be congruent with my image to ask her directly on a date. She responds well to most of my compliance tests(she does stupid shit I ask her to do) so I was thinking of inviting her over to my house to play video games(she will most likely want too, even though she hates it ), but I dont really plan on playing video games for long. I was thinking of getting food then a walk or a movie back at my place. I want to keep it simple.

What do you guys think? Valenties day is coming soon so I don't know when I should invite her over(before Thursday/valentines day/or after valentines day)?

Basically,
1. how do I ask her out on a date without making seem like a date?
2. what are good date Ideas to where we can talk(get into comfort), then escalate?
3. When should I do it?

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Note to self: Don't Trip

Hi buddy,
based on what you say, she seems to be really into you. I have no idea how old you two are, that makes a difference too. I presume quite young.

The best way to take her out without making it sound like a date (nothing wrong with taking girl out on a date, especially if she seems to be into you like this, but I assume you don't want to go so direct. Its good if its not your style). Just think of something you wanted to do, or place you wanted to see, and tell her you going to do or see this, and if she wants to come along. There is a good cinema in Hampstead... called Everyman cinema. Check out whats on... normally I don't go cinemas with girls, but this one has sofas and tables so you can cuddle and shit... and its hardly busy so it offers some privacy. You can get some food there too... it usually impresses girls. My experience anyways.

Don't be on the edge for too long or it will look like you dont have courage to make a move = turn off.
Even if she pulls back, dont worry, she will appreciate you made a move. Be smooth and if she throws some resistance, just smile and act like its no big deal. At the end of the day, there are many indicators that she likes you, so you act on it and she pulls back, only she will look stupid for acting like that. Not you for making a move.

All the best buddy.