Not Data Hi there, having been a bit frustrated myself with how needlessly convoluted Sara's quest has been so far (in one of my rare but - hopefully - constructive criticisms of our beloved content creator
darkhound1 ), I'll try to offer you my two cents on your stuck point.
For me it has worked this way: before Sara can appear at the bar in her white shirt and blue jeans shorts attire (and with a pill in her system), you need to have met her in her red and black dress TWICE and have held her hand BOTH times. If the second times she sends you a naughty sms with a pink toy in it, you're on the right track.
The problem is that even if you've done all that, her attire is still randomized, so save your game before going to bed at the eve of your third saturday with her, save again in the morning, and then skip time until the bar opens: if she's in red and black, reload from before bed; if she's in white and blue, you can safely reload from the morning.
Hope this is clear and helpful enough.
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Quick edit about love levels: at the begining of my second drinking night with Sara (the one that ended with an sms) her love was at 68, but it skyrocketed to 83 by the end of it (including the kiss). I'm not sure about what the precise requirements are, though.