You can get this achievement in the 9th chapter titled "Lost Love".
Head into the bedroom, take the medicine by the bed, then get in the bed and take a nap. When Tiffany arrives, get up and head to the front door to let her in.
The trick here is to be kind and nice to her, without being pushy.
1. Offer her a drink, head over to the area near the fridge, make it and bring it back to her.
2. Offer to find her stuff. One of the boxes is in the bedroom (back left corner from where you enter), the other is to the left of the phone. After getting the first box, put it on the floor next to her, then get the second and repeat.
3. In the conversation that starts choose Reassuring, Sentimental, then Alone.
4. Head over toward the guitar. Turn on the amp, then play the guitar.
5. You need to do well in the QTE's while playing to charm her.
6. Afterwards, try to kiss her.
If you've been successful, this achievement will unlock.