It's an interesting puzzle (one that I'm prepared to put way too much thought into). I'll try.
I looked at the relevant issues again. In the "Go" arc from 'Tec, I think each of the "years ago" bits are supposed to indicate the earliest point shown in the given issue. In #858, the sisters are shown playing soccer, so it's summer, then they move to Belgium when it's winter, and then their 12th birthday is shown, which seems to be in the spring or summer. So that's around an extra year.
In the US, a late spring or summer birthday usually means you graduate high school at 18, and then have your 19th birthday around that time (my birthday's in the summer, and that's what happened to me). So she starts at West Point at 19.
Ring Weekend happens near the beginning of senior year, so she'd have been there 7 semesters. For example, if she started there in August 2000, she'd have been expelled in August 2003. 22 years old when expelled.
Let's say she was pretty stable for a while, but on her 23rd birthday decided to change things; new beginnings and all that.
She enrolls in some classes at Gotham U, meets Renee, goes into a spiral. When Renee dumps her, it's not winter, and Renee indicates she has classes, so it's fall. Kate mentions she dropped out at the "end of last semester", so she's 24 by now.
She meets Batman soon after, and let's say she spent a few months working up to becoming a vigilante and begins sometime early the next year.
Six months of intel and about six months on operations by the time her dad finds out, so she's 25 now. Again, let's say she starts her training on January 1 the following year.
The New 52 adds an extra year to her training, but again it may just be a mistake. Whatever, let's say 28 at the very end of her training.
It seems summer-y by the time she returns to Gotham, so let's say she's 29 by then.
Gets stabbed 48 weeks after starting as Batwoman, or about 11 months, then back at home again about a month later, so 30 by now.
Elegy takes place about a year and a half after the stabbing, and it doesn't look very wintery in Gotham, so it could be in October. 31 now.
The New 52 series starts in winter. So she's not quite 32 yet, but since there's an extra year depicted before the move to Belgium, the timeline could still work. At least, I don't see any glaring problems or anything that a bit of fudging here and there couldn't fix. There's some assumptions in there to be sure but nothing that's unreasonable, I don't think.
That was actually kind of fun!