Not a romance-focused series, but two of its seven-ish protagonists are WLW. Both are part of a space crew making humanity's first trip to Neptune and back.
Mia Story Synopsis:
Mia "Local Lesbian" Wattson

Mia has no time for herself and is sick of living on the Moon. She takes an offer to join the Celestion-5, an experimental space ship, in hopes that she'll finally have some personal space and a chance to visit Earth. That hasn't worked out yet. She instead ended up with noisy, nosy coworkers. Her captain is one of the few people aboard with a sense of professionalism, but as long as she's tied to the chatty new guy, making a good impression on him will be a miracle.
On the bright side, one of her roommates is her sole friend Roxie. But are they truly friends? They've only known each other for a year, and despite opening up to her more than anyone else, Mia is still closed off and reclusive. She knows she'll blend into the background among their more open crewmates, but that's always worked out for the best. Making connections with people? That's more foreign to Mia than Neptune itself.
Roxie Story Synopsis:
Roxie "Pantastic" Allen
A trip to Neptune is once-in-a-lifetime, and when Roxie got the offer, she knew she didn't want to miss tagging along with her good friend Jun. Surprisingly, her friend Mia is also there, too, along with many more adorable friends-to-be! The choice wasn't simple though. This journey will be a long one, an uncertain one. Whether staying or going, she'd be leaving loved ones behind.
Also she's the ship's medic?? The power is enticing, but when she signed up, she did so under the assumption she'd be working under someone more experienced. Many things can go wrong, requiring the expertise of many different doctors, physicians, nurses, and surgeons. Roxie is simply one nurse's aid! Now she finds herself with her new friends' lives in her hands, curing them all with a smile.