How would you feel if your ex got engaged a month or a few after your breakup?

So, obviously this question relates to the Ariana Grande/Pete Davidson/Mac Miller situation. But instead of making it about them, I'd like to know how you would feel if you were in this situation. If you don't know the situation: Ariana Grande announced her split from Mac Miller in the early part of May. A week or two after that, she and her new boyfriend Pete broadcasted their relationship and now they are engaged. Both Ariana and Pete just got put of long term relationships (2 and 4 years). If you were the ex, how would you feel? Personally, I would be upset if my ex gpt over me that quickly enough to get engaged to someone. I love both Ariana and Mac and I know their lives don't affect me. I don't blame Ariana for leaving (she said Mac wasn't sober and the relationship was toxic) and I hope her new relationship brings her happiness, but this feels a little reckless.