[@rivaan] So skill wise - 
Pistols would be considered a specialty skill for her, even though she learned to shoot before she went to the academy. But with her Jack of All Trades (Guns) skill it isn't really needed. You only would have a separate skill if you want her to be say especially gifted with them, as it gives you a higher modifier. (Reason why SciTech people have their field of study as a specialty, in addition to their Jack of All Trades, since it's what they specialized in). 

In her history, you need a full paragraph for why she joined SHIELD.