First Time With Another Girl

Me and my best mate have been inseparable since we met at 11. She's bisexual (although swings more toward girls) but I've always considered myself straight and in fact am engaged. A few weeks ago we were mucking about at hers, she lives with a couple of college buddies, and we decided to print off a couple of porn pics for her housemate as a joke. We're both pretty open about the fact that we view porn and masturbate using it (though I've never looked at it with her or had any sexual experiences with her) but her housemate is incredibly prudish so we thought it'd be funny. She immediately suggested a site, she knew the address so I assume she'd been there before, and before long we were giggling and choosing pictures, and laughing at some of the more bizarre ones, but in truth the whole thing was turning me on. I commented offhand that a picture of two girl's grinding on each other was hot and she looked surprised and joked that she was the bisexual one here. We carried on but a little less exuberantly, both trying to be nonchalant and both turned on, and eventually she conceded "Some of these are pretty hot, aren't they?" She asked me if I was horny and I confessed I was. She squeezed herself through her jeans briefly and now completely desperate to masturbate, I blurted out that I needed to go to the bathroom. "To get yourself off?" She confirmed, and I nodded. "Just do it here. Come on, I'm horny too. We're best mates, we both know we do it, who cares?" She had a point, and I nodded in agreement. "Which one do you like best?" she asked. I took her back to a photo of a girl, back arched and clearly in the middle of an orgasm, with another girl sucking her clit. She stood up and unbuttoned her jeans, pushing them down around her knees and sitting back down. I followed suit, and we both started to rub through our panties. "God that's good" I muttered, and she nodded in agreement. "Does it feel good, with other girls?" I asked her cautiously. "Awesome, much better than guys" she told me, and looked at me "Do you want me to show you? I mean, don't worry, I don't think of you like that you're like a sister to me, but if you want me to show you how it feels I will". I considered it for a second before the horny side of me took over and nodded. "Okay, lie back on the bed" she instructed. I did so and she slid my jeans off and then my panties. She ran her hand up my thigh and I sighed and closed my eyes, and then she eased my legs apart. "It's better if you pull your legs up" she told me, and I did so, stretching my pussy lips open. She paused for a second and I opened my eyes, just as her tongue made contact with my labia. I moaned involuntarily as she ran it up the slit and over my clit, and my muscles clenched with the contact. It felt so good and I was so turned on that I knew I was going to cum hard, and fast. She went back down and lapped around my hole, now oozing copious amounts of juice. "My clit" I mumbled desperately, needing to cum. She grinned and ran her tongue back to it, eliciting another moan from me, and then her tongue planted on it and she began to suck. I cried out loudly, I couldn't help, the feeling was so intense and mind-blowing. My hips arched upwards, thrusting against her, but didn't stop her suckling on my clit with precise rhythm. I can't remember what I was saying but I was crying out something along the lines "Oh God, oh God", and thinking back it was lucky we were the only ones in the house because I had abandoned all sense of volume. It only took about 30 seconds of this and then feeling her fingers push into me and I felt everything moving down around my pussy, my muscle clenching, and I clutched the sheet underneath me and began to cum, grinding myself against her face and fingers. She kept sucking and rubbing my g-spot (which she found instantly) and I lay twitching and crying out with pleasure as I came for a good 20 seconds. Eventually I stopped shaking and grinding and with a couple of playful licks she stopped and pulled her fingers out. I was lying on my back, legs spread, utterly spent. She grinned at me. "Now you can see why I like girls. We have skills" she sniggered. Since then we've done it twice more, me returning the favour the last two times, and whilst we have no intention of having any kind of relationship other than the close friendship we've always known, it's certainly an added bonus!