Here's the guide:
First of all at the start of the level head to the most right area, then jump onto the table and activate the portal. Head into it.
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Then there will be 3 boxes, create a construction that looks something like this, then check this sign and andswer yes to everything. After the third time you quickly have to run to the right side of the screen
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She'll get stuck on boxes if everyting is done right
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Then you carefuly jump on top and lock her up by throwing the top box on the left
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Then you open the chest and get the battery
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After that leave the portal and activate the robot girl
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Then re-enter the blue portal and get the key from the chest (mine's empty since I already got it)
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There maybe is an easier way (you just have sex with the lab girl and THEN you flip the table, launching both the table and her into the stratosphere), but that was the way I did it, so hope it helps.