It doesn't matter which "excuse" you use, so much as it matters that you have context for inviting her over in the first place.
Ex.
You're talking about some great movie which you both like. Then you use it to invite her over. It might look like this:
You & Her: [Conversation about how you both like The Dark Knight]
You: You know...now I kinda feel like watching it. I have it on blue ray/netflix/on my computer. Let's go watch it.
You can use the same process for anything. It could be your dog, having a glass of wine, showing her your guitar, playing a game of checkers...you name it. You can apply this process to any activity you might do in your apartment.
What you SHOULDN'T do is just invite her right out of the blue.
Ex.
You & Her: [Conversation about her hopes dreams etc]
You: Hey, we should go watch a movie at my place.
...In this example, there was no context, no good reason...she still might accept your invite if she's made the logical decision to have sex with you (it is the 3rd date after all!), but it's a much less convincing story for her to tell her logical mind & her friends after the date (which is what plausible deniability is all about).