Weird but sweet behavior

Hi everyone. I have a 1 year old female tuxedo cat. We got her 3 months ago. She is the sweetest cat ever, she doesn't bite, doesn't play with our hands (only toys) and doesn't use her claws at all. But she is not cuddly snd doesn't like to be held anyways which is fine we love her.

The strange thing? Whenever my boyfriend leaves the house suddenly she starts screaming and runs to me and becomes a whole different cat. She starts putting her face on my face, cuddles me, asks for pets and sits next to me until my boyfriend comes back.

Is she having separation anxiety? What is wrong with her? When we got her I was the first person she got attached or basically her safe human because she was really afraid of the new place and wouldn't leave from under the sofa unless I was present.