Dozens of Jess' celebrity friends congratulated her on the happy news, with singer Ben Lee commenting "Maizal Tov" while her sister Lisa wrote "Bling-a-ling to go with your Jing-a-ling."
Recording artist Jaguar Jonze commented "AWWWW YESSSS 🔥" and actress Natalie Imbruglia penned "Congratulations ❤️".
Jess and Alex went public with their romance last year after the Veronicas star split with her longtime fiancé Kai Carlton in October 2020.
The pair hadn't been living together for nearly eight months amid COVID-19 travel restrictions - with Kai residing in Los Angeles and Jess based in Brisbane at the time.
"To all the souls messaging me about Kai – we are no longer together," Jess said when announcing their split. "I was not afforded any real explanation to address this with clarity here."
"While I appreciate your concern, as much of our relationship was on social media, I don't know what to say except that I wish to put this behind me, and I'm lucky to have people who love me to support me through this time," she added in her post.
Watch Below: The Veronicas: Blood Is For Life FIRST LOOK
In October 2019, exactly a year before their breakup, Kai proposed to Jess at a resort in Joshua Tree National Park in Southern California, with Jessica sharing the news on Instagram.
"Even though we are engaged, we won't be able to see each other until the borders are open again because of the government restrictions," Jess said.
"We are doing amazing and I've got the family through all of this."