I think she rushed it without a thought. Maybe after she said to get married it was a same day wedding so nobody was invited except her maid
They didn't specify when he was leaving (highly doubt it was the next day or was it?), and they could've had the ceremony in her family estate (at most they live 2-3 hrs from them?).
They had time to dress up and get to the venue...
It's just frustrating because there were a million other ways this could've been handled, but in order to add in drama the author wrote it like this...I love drama and conflict, but not when it was so obviously shoehorned in...I can't really explain it, but it's a pet peeve I have.
Ripley is impulsive, if you didn't notice. In the novel iirc he left for the war a day after the wedding. Ripley's thoughts was on war and Geronis and her feelings are all mixed of fear, worry and happiness. In that state of mind and feeling, does she even have the time to be thinking of anyone else?
Besides it's her wedding. She's not the OG Ripley and she's definitely not as close to OG's parents. So it's natural that she'd not think of them as often.
To me, it's perfectly natural of how Ripley does it(the wedding rush). It'd be more odd if she were to be calm and composed and prepare everything perfectly in such a short amount of time to officiate the wedding. That's just not her.
Why didn't she invite her parents? If it was regarding time, she could've had someone tell them while they were getting ready, and if she was worried about them objecting, she could've just summon them without telling them what it was about.
Also, who was there to officiate the union? Because unless it was legal, then it was just a big waste of time...
It's unnecessary drama...