Question about Leona

So I just played a Butcher's Bridge against a Leona and have a question about her abilities/runes/masteries...

I couldn't figure out why I was getting stomped so hard so I checked her stats to see what she was building. At level 11 she had a Randuin's Omen, boots of speed, and a Guardian's horn. I also noticed she had nearly 170 AD. I moused over that and found she had +103 AD over base. is there something she can do that would give her that much AD? I mathed it out, and even with a full AD rune page and masteries, she would be nowhere NEAR that. Is there some mechanic I'm missing?