Like I said, principles and beliefs are not easily changed for anyone. In the examples you mention it stands to reason she would slowly change long held deep beliefs. Anyone who snapped theirs fingers and said I just changed my mind on that issue never had any core beliefs.
TPP is just a specific example of the larger position that free trade is beneficial to not only America but all the trading partners. It should be and probably was always the position of anyone involved in negotiating these treaties to get the best deal possible. As in all negotiations there is compromise. I suspect Mr Trumps sees countries as small businesses which can be intimidated into agreeing to treaties which would only benefit America. I believe it is more a case of mathematical economics. As someone says .... do the math.
More broadly, any issue or position which speaks to the national benefit and is firmly based on the Constitution should be a principle worthy of discussion.
Free Trade
Foreign involvement (nation building)
universal healthcare
universal higher education
energy - depletion or renewable
infrastructure - building and maintenance
job creation - job incentives
etc
are these and many more, items which promote the general welfare? these would be my principles
