Sorry to hear the position. I have two experiences, one my own, and the other my brother.
With mine, we had everything joint/shared, but it was amicable - although we reached the point of separating at the start of divorce proceeding and have never met since, and she used a solicitor and I didn’t, we basically split everything 50:50 though recognising some things were really ‘hers’ and others ‘mine’ (hifi mine, but a good few valuable records hers): no argument. (No children, and we had enough cats.) she had clearly instructed her lawyer to keep it fair, and I think only used one because she didn’t want to be directly involved.
My brother, however, was taken to the cleaners by his ex-wife and her expensive lawyers - she came from a wealthy background (though financially the marriage was about equal). Even though the cause was her having an affair, and my brother had custody of the children, and she had a job as a teacher, she had an alimony settlement, and her lawyers demanded more every time my brother got a pay rise (he worked in the public sector, so she knew whenever that happened). She will get half the house if he ever sells it, and she even managed to get a clause through where she was entitled to a half share of my brother’s pension, whether or not he remarried, as long as she didn’t marry, so now he is retired he is on a pretty tight budget, and daren’t even consider selling the house either to move away or to downsize. 10 years later she isn’t married, but has lives with the person she had an affair with, having moved in with him immediately.
So, my advice would be to protect what you can immediately just in case - split any joint accounts etc. Try to have neither of you use lawyers - they can be the source of ideas to benefit their client without the slightest care for the other party. In Britain at least, if there is nothing complicating matters, e.g. like children, and if the divorcing couple are capable of talking (or writing) and agreeing, then it is perfectly possible and quite straightforward without a lawyer. But if she gets one and demands start ramping up, get yourself the very best one you can afford - you might not be able to afford not to. (And if the lawyer demands more than you think is fair for you, you can always backtrack just before it is signed sealed and delivered).
Good luck if it goes to divorce.
But some people find a future - a happy one - even after an affair, despite how impossible it may seem. In part that may depend on the circumstances of the affair, and how much you the two of you want it to work (and maybe at the early stage, how much she actually wants it to work). If that is even a possibility, if you still have feelings for her and wish it was different, and if she clearly wants to get through this, then I urge you to try marriage guidance counselling - Relate or whatever they call themselves. It worked for a close friend of mine, he being the one that had an affair, and now he and his wife are stronger and closer that ever before.
Good luck if you try to find a new future together,