Is my cat stressed? Please help.?

She seems to get scared from loud noises. She meows like soemthings wrong every no and again. And her tail poofs up for no reason. She seems like she wants to be outside but if i let her my mom will be pissed and my kitten won't have much of a playmate. I only had her for about 3 mos and she's nine mos now. The people who sold her to me told me she was 4 mos but when i took her into the he said 7 mos. They lied about alot of other things too so i don't know if she's an outdoor cat or 100% indoor cat. Cuz if she's outdoor my mom won't let me keep her. She seems to spend her days my the gate and windows. If she's stressed how can i know and calm her and help relieve her stress pls help cuz its making me stresse