Maybe after you've proved to Susie that you won't always keep her insecure, she'll be willing to be friends with Rachel, but don't bet on it. You and Rachel sound pretty tight, by the way, and even kind of compatible. Maybe she'd be secure enough to handle you having women drinking buddies. Most women aren't. If you want the benefits of a lasting, loving relationship, you're probably going to have to give up some of your bachelor freedoms.
Some men are incurable philanderers.
You can be the wildest, the most imaginative and the most satisfying partner in bed, and it doesn't matter. A philanderer will leave your place and, within a block, make an illegal U-turn in front of a Mack truck to chase a new conquest he sees driving in the opposite direction. I had one of these types once. One night we had a great love-making session, and the next thing I knew, he'd backed his car over my new puppy in the driveway, sneaking out to see another woman. Sometimes womanizers grow up and grow out of it, but it can take years.