Am I overreacting to my boyfriend’s ex-crush hearting his message?

I’ve been with my boyfriend for a little over six months. In general, I’m not a jealous person, but I do have boundaries. I’m completely fine with him going on vacation with his friends or going out for a night with them, so I’m not a controlling or difficult girlfriend. However, he has a female friend. They’ve known each other for about three years. Lately (for more than six months), they barely talk and don’t really see each other anymore. Yesterday, she texted him about his exam results. He failed and has to retake one of his exams. She wished him good luck, he said thank you, and then she reacted to his message with a heart emoji. I saw it and got really upset because my boyfriend used to have a crush on her. Also, since they aren’t even close friends anymore, I found it strange that she sent him a heart. Am I overreacting?

Am I overreacting to my boyfriend’s ex-crush hearting his message?
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