Not just any woman, but you're ex gf calls you boo...but you're unsure how you meant it; help?

It was in the context of goodnight text message. Today was the first time we met up since Christmas. She said to me, "you look hot." I said "I know it's hot outside" but she interrupts and says "no, I mean you look hot, you look good sitting in your car like that". So she meant the hott looks. Anyhow, she is a teaser but I think she could be hungry. We both may be realizing we really love each other and maintain feelings for each other. I got off track, my question is "what does boo mean?" Or what could it mean?