Would you really describe her as an amateur? She is just some girl you have hijacked twitter/instagram photos from.
And your point is?
The girl loves to pose, and she posts her pictures on twitter where anyone can view them. Hardly hijacking, more like redistribution. So what is the big deal about me posting them here?
As she does not pose professionally I regard her as an amateur. If you want to get into semantics then we shall have to describe everyone on here as a definitive sub-category. Professional, semi-professional, amateur, semi-amateur, psuedo-amateur etc...
Personally I try to keep it simple.
I take it you are going to say similar things to others on here who post pictures of non-professional models? Like Liam in the Alexa Attias thread for example?
Hey, if anyone doesn't want me to post any more pics of her, let me know. I'll go with majority rule...
Mod edit: don't worry about semantics. To my thinking, any gal just posting selfies for her own promotional/ego/entertainment reasons IS an 'amateur' in the practical sense... as opposed to models doing photoshoots and/or videos for pay. Regardless of definitions, users enjoy your posts/pix immensely and as long as they're OK per the Owner's rules (as all these are) they're 110% welcome salem! 
-Palomine