"I have been crying on & and off all day. I don't know that I can properly form adequate words to express how much the love and support means, but I just want to say thank you," Becca wrote via Instagram Stories on Friday.
"And to everyone who has known about us for the last 4 years and gave us the time and space to do it in our own time -- the magnitude of that alone is not lost on me. I am so grateful."
The Bachelor alum continued, "Hayley, thank you for showing me how to be brave and how to love myself. I'm so glad I don't have to avoid pronouns on the podcast now. I love you."
Becca introduced her romance with Hayley to the world on Friday by tweeting "3rd time's a charm" and posting an Instagram video of their sweet moments together over the years, which she captioned, "Hard to say if this is a hard or soft launch, but it is a launch."
Hayley, who is very open about her sexuality, replied in the Instagram comments, "The best four years ever. I love you Becca."
Becca going Instagram official with Hayley came only hours after Becca -- who co-hosts the "Scrubbing In" podcast -- kissed Hayley onstage in front of an audience at a party held in West Hollywood, CA, on Thursday, People reported.
"It was Hayley's night but it became Becca's night too because she came out publicly with the kiss," a source told Us Weekly last week.
Becca and Hayley were celebrating the release of the singer's new "For the Girls" music video, which was released on Friday and is the first single from Hayley's upcoming album, Panorama, out this summer.
The "For the Girls" video is a spoof of The Bachelor franchise, showing Hayley as the lead meeting a lineup of women with crazy limo entrances outside of a mansion.
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The video ends with Becca stepping out of a limo in a gold off-the-shoulder dress with a high slit and smiling at the musician.
Rumors that Becca and Hayley were dating have circulated online for years, however neither woman had ever publicly confirmed the relationship before now.
Becca and Hayley were photographed together at NYLON's Annual Young Hollywood party in May 2018, People reported, and that same year, Becca confirmed she was off the market.
Becca then revealed on her podcast in 2019 that she was "in love" with someone, and she subsequently admitted to Us in September of that year that she wanted to keep her relationship "private" and all her "own."
"I had a public relationship before and it just felt like I had a lot of people involved, which I know that's why they sort of watched me in the first place," Becca said.
At that time, Becca wasn't sure when she'd publicly identify her partner. She said she felt protective of her romance and had reasons why she was keeping it under wraps.
"I just feel if the moment comes where I'm like, 'Oh, I'm just going to say something,' then I will," Becca told the magazine. "I'm really happy and I hope to eventually start opening up about it more, but I'm happy with it being private right now."
In 2019, the Louisiana native said she had yet to introduce her private love to her parents.
"My family lives far away, so my sisters I guess have been introduced, but not the rest of my family," she told Us in November 2019. "I'm really happy. I'm in a really good place."
Becca began dating The Bachelorette 9 and Bachelor in Paradise 1 alum Robert Graham in December 2016.
"It's fun. We've been friends for a long time and it was just a natural progression, and he's just amazing and been patient with me," Becca told Us that month.
"I need someone that's patient and willing to deal with me, and he's been that way. So it's been fun, it's been an easy transition."
But Becca and Robert broke up in May 2017, with Becca later revealing she had been working and traveling too much to be in a committed relationship.
"[The breakup] was more of me just wanting to take this time for myself and focus on me and what I'm doing," she told Us in September 2017. "It wasn't like one of us cheated or there was this bitterness. I still care a lot about him and there's no hard feelings."
Becca hoped Robert felt the same way and would say the same thing.