The Rambam advances a philosophical argument against this concept of “bashert” as well. The Rambam holds that getting married is a mitzvah. Without the ability to choose whether to do a mitzvah or not, fundamental ideas like schar v’onesh make no sense. Free will is Judaism 101. If it was predetermined that “Bas Ploni l’Ploni,” it would mean a person had no free choice whether or not to fulfill the mitzvah of marriage.
When a statement in Chazal like “Bas Ploni l’Ploni” contradicts a pasuk or a basic tenet of hashkafa, it means (in the Rambam’s view) that statement is not meant to be taken literally. We may be born with a predisposition to enjoy the company of one type person over that of another and that may direct us toward choosing one individual over another as our spouse, but by no means is there one specific Mr. or Mrs. Right out there for anyone.
Now for the most important point that's the take away lesson. The Rambam says that it’s mefurash in Chazal that your spouse it not determined by Heaven, and he quotes a gemara that we would probably interpret exactly the opposite of the way he does: “Hakol b’ydei shamayim chutz m’yiras shamayim.” Doesn’t that mean that who your spouse is and most everything else in life – “hakol b’ydei shamayim” -- is in fact predetermined? No, says the Rambam. Your marriage, your job, where you live, etc. are all parts of the exception. Who we choose to marry and how we live our married lives is all about finding the means to grow in yiras shamayim. It's all part of the "chutz..." part of the equation that is in our hands alone.
Based on this Rambam perhaps we can read Adam’s response to Hashem when he is accused of eating from the eitz hada’as a little differently than the usual pshat. Adam blames his mistake on, “Ha’isha asher nasata imadi…,” the wife that you, Hashem, gave me. Adam was perhaps saying that because Chavah was given to him – he had no choice – he was deprived of an opportunity to grow in yiras shamayim and that contributed to his downfall.