"It's true that Ariana has been struggling a bit with life in general," a source told PEOPLE after Miller's death. "It was devastating and shocking to her. It's had a huge, negative impact on her life. It made her rethink many things in her life."
The insider explained that her imminent marriage was one of those priorities she had to rethink. "She realized that planning a wedding right now felt very rushed. It's not what she wants to do right now. She doesn't want to make any rushed decisions and has decided to take a step back instead."
A different source — someone close to Davidson — put the recent events into perspective. "They're dealing with things that people wouldn't have to deal with in a lifetime — an ex-boyfriend reportedly overdosing and having all of this fame and attention. These followers and living their lives on social media ... it's a different world."
As previously reported, Grande and Davidson's whirlwind romance came to a screeching halt over the weekend, about a month after Miller, who Grande dated for years, reportedly died of an accidental overdose at age 26. Davidson, 24, and Grande, 25, started dating in May, the same month she ended things with Miller — and they were engaged by mid-June.
The day after Miller's death, Grande paid tribute to him on social media, sharing a black-and-white photo of him with no caption. About a week later, she shared a throwback video of him and her laughing together and opened up how much he meant to her.
"i adored you from the day i met you when i was nineteen and i always will," she wrote. "i can't believe you aren't here anymore. really can't wrap my head around it. we talked about this. so many times. i'm so mad, i'm so sad i don't know what to do. you were my dearest friend. for so long. above anything else. i'm so sorry i couldn't fix or take your pain away. i really wanted to. the kindest, sweetest soul with demons he never deserved. i hope you're okay now. rest."
A source told TMZ that Miller's death was the "breaking point" in Grande and Davidson's breakup, saying that Grande was in an "incredibly dark place" following the overdose and that she couldn't be "fully invested" in her engagement.
Despite concerning fans with an emotional series of tweets saying she was "so f—ing tired" and hinting that she wouldn't be touring for a long time, Grande is expected to return to TV with a performance during an upcoming special for Wicked's 15th anniversary.
"Honored to be included in this celebration of 15 years of my favorite musical of all time," Grande tweeted on Monday, the day after the breakup news surfaced. "Wouldn't miss it for the whole universe #wicked15."
The performance will air on Oct. 29, the same month she dropped out of a scheduled performance at the F— Cancer Barbara Berlanti Heroes Gala in Los Angeles. Her manager, Scooter Braun, delivered the news during the event.
"Someone that I am very close to could not be here today because of things that she is going through," he said. "She couldn't be here today, and while I was frustrated, being a manager, my wife, being who she always is, said to me, 'She needs this time.'"