Flowers are a perfectly nice gesture and, on their own, a fairly forgettable gift — gone within the week, rarely brought up again. If you want something that actually stays with her, the answer usually isn't to spend more. It's to be more specific.
Something built entirely around her, not "women" generally
At Galaxiana, you can name a star and write a message that could only ever be about her — not a line that would work equally well for anyone. From $34.99, and noticeably harder to mistake for an afterthought.
Reference something she mentioned once, in passing
The book she said she wanted "eventually." The place she keeps saying she'd like to see. The hobby she keeps meaning to start. Remembering small, throwaway comments — and acting on them — tends to land far harder than anything chosen off a list.
Protect an entire afternoon for her, properly
Not a rushed dinner squeezed between errands — actual, unscheduled time, spent doing whatever she'd genuinely choose. Time is harder to give than objects, and remembered considerably longer.
What she'll likely remember isn't the price tag. It's whether, out of everything you could have picked, you picked something that could only have been meant for her.