And they are likely to riposte that facts about her UF are naturalistic just because they can be inferred from her behaviour.

But this is false, surely. I take it that a fact about X's UF might be some such as 'X prefers apples to pears'. First, notice that X may also prefer his/her philosophy TA to his/her chemistry TA. X has different designs on the TA than on the apple. So, properly stated, preferences are orderings of desires, the objects of which are states of affairs rather than simple things (X desires that X eat an apple more than that X eat a pear). Second, to impute desires such as these requires also imputing beliefs (you observe the apple gathering behaviour -naturalistically unproblematic- but you also need to impute to X the belief that the things gathered are apples. X might be picking the apples thinking they are pears). There's any number of ways to attribute beliefs and desires in a manner consistent with the behaviour. No collection of merely naturalistic facts will constrain these. There have been lots of theories advanced which try, but the concensus, I think, is that there is no easy naturalistic solution.