If you told the rejector that you wanted to end your life without the intention of manipulating them, it's not manipulation. You were just telling the truth.
If you told them with the intention of manipulating them, it's not in itself something good, but it was also something coming of an intense need you had, which makes it a lot more forgivable. Like if someone is on fire, and they try to guilt trip someone into throwing a bucket of water on them, or a starving person stealing some food. These things are not good in themselves, but also the sort of thing that anyone would do if they were in the same position. It's something very much different than, for example, someone manipulating a person into taking a subprime mortgage loan because they want to make money to buy a new sports car or take a skiing vacation in Switzerland.
I don't think you have anything to be ashamed of and I hope you'll talk to your therapist about this.