You're not the only one. I've had this a few times. At her old office, I could sometimes hear them talk. I couldn't hear what they were saying, but I could hear voices. And I would feel jealous and insecure. That other person must talk more than me and therefore must be an ''easier'' client.
There were a few times when I sat in the waiting room and I saw the client before me leave her room, after their endtime, which is also something that makes me feel so jealous and insecure. And just how those clients said goodbye and how my T responded to that made me so jealous and I was convinced that T must find those clients much more likeable than me. At two or three times when that happened I even had to cry.
There was also one times after session. I was waiting for something and my T came to get the client who was after me. And the way how my T greeted her and asked her if she wanted tea... I got so jealous and so angry. I wanted to quit therapy with her.

I haven't told my T that. I did once talked about that I'm afraid she like her other clients more and that they must be more interesting and I must be boring and annoying because I don't say a lot. ut she didn't exactly said that she did like me or that she didn't find me annoying. Just something like I shouldn't compare myself to others, you can't compare your therapy to someone's elses therapy, every person is different and does their things on their own times and you (I) are just a person who doesn't talk a lot, that is jut you and there's nothing wrong with that.
At the moment I don't feel so much envy toward other clients, but that could come back. But my jealousy with my current T only started this year. I dídn't had it before. I did had once in a group therapy, but that was because other clients got more attention. Because I was so quiet, I was ''easy''. I wouldn't speak my mind if something bothered me, so they could give me little attention and I wouldn't complain.