Be bold. Fucking go for it.
If you’ve never texted her before, send her a text that tells her A. you’re interested in her and B. asks her if she’s interested in doing a specific, concrete activity with you at a specific, concrete time.
Don’t ask if she wants to do “something” “sometime”. Instead, ask her if she wants to get Mexican food at 7pm on Friday. Or if she wants to go for a hike with you in X nature preserve on Sunday at 11 am.
Don’t be hesitant. This is about you specifically stating what you want (aka, to spend more time with her in a 1 on 1 setting), and asking her if she’s also interested.
That’s it. That’s as complicated as it needs to be. Either she’s into it, or she isn’t. But I can tell you one thing: she’s much more likely to be interested in going out with you if you’re decisive, bold, and give her a definite plan, than if you give her some mealymouthed maybe sometime we should see each other.