Hello, I have been riding horses for many years and have a dead broke reining mare. I decided it was time for a new challenge so I bought a yearling filly. My question is how much can I work with her and what is to much for her? She is very halter broke, good with feet, ties, stalls, trailers and knows how to lunge. I bought my reining horse dead broke at 3 and I am hoping for the same with this horse. (I know I will be judged for this) Any information would be helpful as this is my first time breaking a horse.
Yearlings have very short attention spans - I did not do much more than groom, tie, lead, and make sure my yearling was good with farrier/vet/dentist. Generally, while teaching anything new, I kept it to 20 minutes or less - make positive progress before the yearling gets bored/distracted/impatient and call it a day. Let her grow up and strengthen her body by playing with other horses in the field.
Don't begin destroying her growing joints by lunging her often.
I am not judging you about having a dead broke 3 year old, but I would personally not follow the same path. My young horse was not mentally mature enough to have any big expectations under saddle until he was at least 4 years old. I saddle broke him at 3, did basic trail rides until 4, and then began teaching him 'real' stuff. The trend of having a finished 3 year old for reining futurities needs to die out, imo. It is a good way to create a lame teenage horse, and a dead brained one. There is plenty of science supporting that most horses should be started later on than most people do, because of their legs and spines maturing later than 3 years old. I'm not going to continue harping on this, as you can do the research yourself and decide what is the best for you horse.
Once she gets a bit older, you can start doing more groundwork and introducing tack and the bridle, but I wouldn't be so urgent to introduce a rider because of my points above. Give her time to mature still and be comfortable with everything that you are doing. If your raise her right and don't sour her from the beginning, you can raise a horse that will do anything for you with pleasure and try, rather than just having a dead-minded, push button 3 year old.
Heck, really my only point with this post is don't rush your young horse's life. There is no real reason to, and I'm sure others will chime in. Be patient and you will have a lot more horse for a lot longer of a time, with a lot more try for you.