Yes, she's probably ready. I think the most important criterion in deciding whether or not to try learning to use a knife is willingness to follow directions. If she's not listening to and obeying every word you say, no knife practice, period. That and sufficient gross motor and fine motor skills to control the knife would be important. If she can handle butter knives and isn't a super-clumbsy kid, she's probably ready. Even my 2 1/2 year old begs to learn how to cut vegetables, and we've been beginning to work on learning to cut them together, and that has gone well for us.
Obviously, you may want to have her watch you first up close and see how you cut, and have a dialog going about how you use the knife properly (probably every time you cut), which side of the blade is sharp/used for cutting, where your fingers should be when you cut, how you don't want your fingers near the blade, how you should cut slowly and carefully rather than quickly and carelessly, etc. When I was first teaching my son how to hold the knife to cut, I had him put his hand on the handle, and then I put my hand around his, and I held the veggies, and we cut together, so he could get the feel of a chopping motion, while I was steadying the knife to make sure it went where it was supposed to...build that muscle memory of what chopping should feel like. From that level of joint chopping, you can increase the independence, let her position her other hand safely to hold the veggies, and then help her get the knife in position, and let her do the slicing, and so forth until she's doing every part if it without assistance. Make sure she's standing somewhere stable and is situated high enough to see what she's doing. Stand on a chair or at a lower surface like the table if needed.
Additionally, I would note to match the type of knife to the task at hand. A small knife like a paring knife is going to be much easier for a small child to control, but it doesn't have the heft and weight of a large knife, so it will actually be harder to chop hard vegetables like carrots with than a chef's knife. So if you'd like to stick to starting cutting practice with small knives, make sure you pick something fairly soft (eg: strawberries, bananas, peeled cucumber, etc) that will not require fighting the tool.
And of course, remind her every time you practice that it's very important to have mommy's help when you're cutting with sharp knives so you don't get hurt, and that she needs to come get you and have you "watch" (ie: help to the degree needed) if she wants to cut something, no using the knife alone when you aren't watching. At least, until she's fully mastered using knives.
If she really wants to learn to use the knife, she will probably be very willing to pay close attention to all the rules that go with cutting, and be willing to learn them. And if not, put the knife away for a while and try again a different week or month.