no i don't think she would have gotten his trust either way. his wounds are deep. he's not going to trust her whether she tells him up front or not. What would have most likely happen if she had been upfront about it, the Shield Hero would have tried his best to not let his identity be discovered and try his best to get rid of her or he wouldn't have even bother to help her in the first place. it wouldn't have gone good either way.
another thing i think she didn't tell others about her identity is because of her sister. The younger princess knows the older princess is evil and bad and she knows that other ppl knows that too. She probably got discriminated against for being part of that family exactly like what the Shield Hero did. this is just something i thought of as a possibility
hmm. i think the princess would of gotten his trust if her other family members didn't treat him like crap and also didn't hide her identity from him. if she did want to be friends with them, she should of realized how to go the right way to approaching them. she would of been a good ally for them, but anyways, i kinda look forward to seeing the other countries.