I don't think Kara is honest with Sam about the cheating as much as she just doesn't attempt to keep it from him, the way Lee does. But. The reason I judge Lee more harshly than Kara is mostly about authorial intent, for me. It's, like, I can get over Faith MURDERING people, but I can't overlook the fact that Buffy once tried to unsuccessfully kill a human being. Because the first is acknowledged by canon as being horrible, but the second is totally overlooked. Kara's cheating is still seen by canon as cheating, while I can't help but feel that Ron wants me to see Lee as the morally upright person who wouldn't cheat and Kara as the temptress who does this, apparently, all the time. I know cut scenes aren't canon, but the fact that that one scene was there means that there was SOMEONE there who was reading it that way at some point. Which, well, has more to do with my inability to go along with authorial intent on things like these and feeling the need to rebel out of spite than actual canon maybe? ;)

In closing: there is a sexist double-standard in this fandom: Sam gets a free pass because he looooves Kara sooooooo much. And she loves him! So it's totally ok for him to forgive her and take her back. But Dee? Totally weak and stupid (and other words I would like to punch people for).

So I have never actually participated in the BSG fandom at large, but I thought Sam was also generally seen as weak for putting up with Kara's batshitery?

But, yeah, I've always seen Dee as one of the stronger characters on the show and marrying Lee and staying in that marriage to work things out have both contributed to that perception for me.