Really, yes, 3 months is too young. Human babies are meant to nurse almost continuously in the early months. Our milk is very dilute. It is perfect food, and almost entirely digested and utilized by the body.
Sometime around the middle of the first year does not mean right on the 4th month birthday! Many babeis are not ready til 8, 9 or even more months. Sometimes over a yr, 14 mos. It can take 2 yrs before a child is really eating table foods as an impt part of theri diet. And this is normaland healthy as long as they are bfing.
A young baby such as yours will not be able to "digest" table food. it will simply pass thru her system, and out the other end, actually robbing her of calories to do the work of passing it thru. It can then cause constipation, gas, and parhaps an allergic reaction.
Women of an earlier generation fed their babies solids way to early. Drs knew how poor in nutrition those early artificial milks were. Condensed milk and Karo syrup. No extra vits or minerals. So they tried to make up the difference with table foods. Moms fed their newborns orange and tomato juice for Vit C! Then commercialism got on the bandwagon and the public believed all the PR
We have so much more research available now. In fact, the very latest studies show that fully bfed babies, who do not start table foods until 8 months, have the best iron levels at one yr, when compared to other feeding methods (partially bfed, artificially fed, or early solids).
At the turn of the 19-20th century, drs told moms not to start table foods until one year, and to nurse for at least 2 yrs, as there were all kinds of diseases with no treatment except prevention thru bfing. Then, antibiotics were invented. Then, industrialization invented a safer rubber nipple and glass bottle. Etc. Downward spiral, cut to WW2, women going to work, suddenly artificial feeding was seen as *superior* to human milk!
Read: Milk Money and Madness. For all this info and more.