It sounds like he broke an agreement with you (no touching while naked) and that's what's most important here in my opinion.
I now do not trust my friend's intentions if she can lie to her husband about her trying to find intimacy over at our house.
Does your partner know about your concerns now? Do you think this makes only her less trustworthy, or does it makes your partner less trustworthy, too? He seems to be complicit in her lying, after all.
If her husband would probably be upset, then it's probably cheating, regardless of how your partner has tried to justify it.
The rightness or wrongness of "enabling" cheating is a complicated ethical debate in the non-monogamy community. My personal experience is that polyfolk are more likely to think enabling cheating is wrong. Some people take the position that it's not their relationships and so not their responsibility. Personally, I wouldn't knowingly enable cheating.
Some threads to consider: Honesty in poly
and Poly? Coverup for Cheating