Searching for a lesbian story

There's a lot of these so I'll try to give a lot of details to find this particular story. It's about twilight having to teach and educate her ex nemesis Trixie through sexual means. I believe she's forced to wear a collar that suppresses her magic. Twilight has her tied to a Pole in her house and has her friend visit. Later on the two start to bond and get romantic. One day twilight's mom visits and wonders why twilight is wearing panties with Trixie's cutie mark on it. Another scene the two were in bed and were about to get sexual until twilight's dad bursts in the room and sees them, then immediately leaves. Twilight tries to talk to him but he ignores what just happened.