From one cat breeder's site:


Different queens will exhibit different signs of being in heat or estrus. Unlike dogs, cats rarely show signs of vaginal bleeding during estrus.
However, their behavior changes greatly, with the majority of queens becoming quite vocal and loud, and showing increased signs of affection.
They may roll around on the floor or plop down right in front of you as you are walking; they constantly want to be with you and be stroked, and
when you pet them on their back, they will raise their rear end up high and knead with their front paws.

So ... maybe! I'd be EXTREMELY careful about keeping her indoors right now. My brother's small son let "Midnight" out cause she was meowing a lot - the subsequent kittens all found homes, THEN Midnight got fixed.