At a year, you don't need to substitute cow's milk for breastfeeds - some moms never give cow's milk at all. You just want to make sure that somewhere in the day, your lo is getting the same sorts of nutrients that she'll now be missing from BM. So fluids, protein, calcium, etc... Cow's milk can be an easy substitute, but you can just offer it with meals, if you prefer. When dropping breastfeeds, I'd suggest trying to do it gradually, to avoid things like engorgement for you.
If you wanted, you could always try keeping that morning feed and drop the rest, then see how you do. You said you're training - have you been limiting your calorie intake as well? If that's not necessary as part of your training regimen, you might find that just one breastfeed during the day won't tax your system too much.