Bertens's general path since she first rose in 2016 has been a general cycle of getting good results when people don't expect them her, causing people to develop expectations for her, flopping when their are expectations on her, causing expectations of her to fall, then starting the cycle over getting good results when their aren't expectations on her.
She has had two good slam results. First an SF at RG in 2016, when people did see her as an elite player yet and there were no expectations of her. Since then people have seen her an elite clay courter and RG contender and she has not been able to perform, despite doing well in lead up events.
At Wimbledon last year, she was perceived as a soft seed because she was supposedly clay courter who was not good on grass and she was able to make it to the quarterfinals. Of course, after making the QFs last year and getting to the SFs of Eastbourne this year she was perceived as a contender on grass and there were expectations on her, so she failed.
Her win in Cincinnati last years was also a surprise to most as she was not perceived as an elite player on hard, but after the win that changed and there was talk about her as a contender of the US Open, so naturally she lost early there (and at the AO as well).
This has been a pretty consistent pattern with her for the last three years. We will see if she is able to eventually overcome it, but for now it looks like her only chance to win a slam is to come in on a 5 match losing streak.