There are advantages to retaining the better heifer calves from your herd and raising them as replacements. One of the primary ones is that you know their lineage -- their genetic makeup -- their parentage. You also know how they have been handled from birth if you keep good records. This should give you an indicator of how their progeny will perform -- from birth weight to weaning weight and ultimately to either a selling weight or retention into the herd.
Selecting replacements can be very technical through the use of various tools available to good ranchers. DNA samples can be taken and analyzed for some of the desirable characteristics that one would wish to bring into their cattle herd and records can be analyzed to "predict" their performance. Or, the animal can be visually appraised and selected merely on how it looks. Things like: Does it have good muscling? Is it at a desirable size based on its age?
If a replacement female is purchased, the same selection criteria come into play. Can records be obtained that would give good indication of future performance? Does the animal have the visual characteristics you are looking for? What does its DNA profile indicate?
Ultimately, though, there is a chance that one will be disappointed in the outcome. No matter how carefully one considers each animal and the available information, they won't all perform as predicted. It is just "educated" guesswork.
It's a lot like many things in life. Decisions are based on imperfect knowledge. Usually we don't think much about them unless they have long-term implications or are concerned with large sums of money. We make decisions every day. Some are just educated guesses. Some turn out better than others.
Many people that I know agonize over even the smallest decision. They become almost paralyzed with fear that they will make the wrong choice. I think a part of wisdom is knowing that you won't always make the right choice, but, with any choice there is opportunity to learn and frequently to benefit. As my friend Neal likes to say, "The secret to making good decisions is to make one. If it isn't the right decision you make another."
I like the way Paul says it in Romans 8:28
28 And we know that in all things God works for the good of those who love him, who[a] have been called according to his purpose.
To me, that verse says that whatever the decision, God will use it for our good.
Should I keep her??