Why would my cat act like this?

I have a cat, she’s about 2–3 years old, and I’ve had her for maybe 1.5 years or so.

When she is in my apartment, she acts very skiddish, and shys away from anyone trying to approach her, to include myself. The only way I can ever get her, is if she is sleeping, and I go up to her then…or I will follow her into my room, and shut the door behind me. Once I get to her, and pet her, she acts perfectly fine, purrs a lot, moves around and clearly enjoys the attention. Sometimes when I’m petting her, she’ll quickly go from purrs to, swatting at me, and being angry for no apparent reason. I have a tall kitty condo for her to climb into, and she’ll get all the way to the top, and lay down. I try to pet her there, and she gets very defensive and angry and does the swatting, and squints her eyes like I’m going to smack her. Both my cats sleep with me at night near my legs too.

I don’t abuse my cat in any way, in fact most people would say I spoil them pretty bad. I have two cats, one female, one male, both bengal breed.

When I took her recently to a cat clinic to have her looked at for some coughing and sneezing she’s had lately, we were in the examination room. And she was very social, walked around rubbing into everything, and let everyone pet her. Not once did she get defensive, or angry, and not once tried to bite, or swat at anyone.

Why would she act so differently at home?