if you have a good master, as far as I am concerned, he will be loving, reassuring and consistently willing to show you he is not replacing you. Your master is wanting to bond with this woman and it is his command to do so. You must follow and trust him if you are to stay in your arrangement.
I hope he is a good and worthy Master. This is a very tricky arrangement he has set up and it could be quite damaging to you. I hope he is the type that allows you to have your time to speak and be listened to. A submissive can only be a good submissive if they are respected. It's a two way relationships dynamic, not one. I hope this is what is happening in this case.
As to being bisexual? If you want to have sex with her and are attracted then yes, you may well be. If you are wanting your Masters attention and support and think you will get it by being in the bed with them, then, likely you are not necessarily.
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