re: Just started a Breaking Bad rewatch - Spoilers

Skylar was flirting with Ted loooooong before she found out about Walt's dealings. She had no consideration to the fact that Walt's cancer had an a dramatic effect on his psyche. Instead, being the self-absorbed shrew that she is, she made it about her.

Terminal illness changes people. As a spouse, you don't say "My husband is acting weird. I'm gonna flirt with another guy".

Also, had Walt's ascension was via legal venture instead of cooking meth, Skyler's actions would not have been much different. It was mainly about control for her. 16 years she was wearing the pants, and once Walt grew a pair she couldn't handle it.