It called extended breastfeeding. You can research it online.
I breastfed both my kids, and let them Self-Wean.
My daughter did so at about 2.5 years old. My son at about 1 year old.
You said you nurse "exclusively." Do you mean that your girl does not get any whole milk? Just breastmilk?
My both my kids, after 1 year old, drank organic whole milk as well. Even though I still had lots of breastmilk. It was a natural transition.
Now, if you want to wean your daughter... then perhaps transition her to whole milk, or what you think is appropriate per your Pediatrician.
For me, I only nursed on demand when my kids were younger... but after a time, I only nursed IF they asked. Not as a matter of routine. In time, the child naturally will "ask" less and less. And your breastmilk output will adjust. ie: supply and demand.
I chose to self-wean my kids. BUT... with my daughter since she was more attached... I talked with her about it. "One day you will not need to drink from Mommy.... you are a big girl.... etc." AND, I only nursed her IF she asked... AND only let her latch on for a short time... not using me as a pacifier and just hanging on my breasts for eternity.
Also, when she got older at about 1.5 years old, I taught her
"MANNERS" about it... ie: ask politely, do NOT just tug my shirt up and grab me... do NOT do that in public, ONLY at home is where you can nurse etc. Otherwise, a child just tends to "grab" and get bossy about it. So, I just in a comforting way, TAUGHT my daughter about how to be polite about it. AND... if she asked to nurse, I would sometimes say something like "Mommy is busy right now... in a minute, okay?" And then I would NOT sit down... but make like I am "busy" (which I was) and just stayed standing and doing stuff. THEN, if she still wanted/needed to nurse, then fine, I sat down and she would. But by that age, she did NOT stay attached to my breasts for very long. Just a couple of minutes... so this was HER way of "self-weaning." That is how a child self-weans... they gradually stay at the breast less and less, and the interval between nursings gets longer and longer as well.
At this age... you do NOT necessarily "have to" nurse "on demand." She is nearly 2 years old. But I know some Moms do. The rationale being that the child is ALSO getting whole milk/other dairy in their diet as well nutritionally, and other solid regular foods by 2 years old. Which is the case of how my kids were.
My friends, put Band-Aids on their nipples, to wean their kids. And they said it worked for them. They simply said to their toddler "Mommy has a boo-boo...." or, "Mommy doesn't have milk anymore..." etc.
Or, some Moms only "allow" nursing at night-time... by teaching their child that when the sun goes down, this is the time. Not during daytime.
Just some ideas, and how my kids self-weaned. For my kids and self-weaning, I did not 'force' them to do so or by a certain deadline... but in my daughter's case, I coaxed her and we would talk about it. And then when she was about 2.5 years old, just one day all on her own she told me "I don't drink from you anymore..." and she giggled like she couldn't believe she was still breastfeeding. And that was it. She stopped, completely. On her own. My son just stopped on his own right away and just did NOT want to nurse anymore either, when he was about 1 year old. Each child being different.
All the best,
Susan