Is it normal my girlfriend gives happy endings?

Pardon me mam, but aint she parton.
She a bit old, still might be ok for a cock massage if her big hooters don't get in the way

So just to be clear! You’re not actually bothered about her wanking them off, just so long as they don’t have a groap of her arse while she’s doing it. But she already told you she doesn’t allow that so what’s the big deal? You seem to have unhealthy trust issues and to be honest even if she does let them have a little feel of her arse so what, it is hers after all.

Lots of stuff goes on in relationships that nobody outside the relationship is ever aware of, and sometimes that stuff doesn't comply with what the culture the couple belongs to deems "normal". You seem to have processed what you recently learned about your gf, weighed up the positives and negatives and come to a rational decision about what you should do rather than stomping out the door. That seems to me sensible.

A couple of points you might want to consider with regard to her coming home from work sexually aroused and with damp underwear:

Researchers have found that vaginal lubrication is triggered by the woman's brain interpreting a situation as being sexually "relevant". Vaginal lubrication doesn't necessarily mean that the woman is feeling aroused in the sense that she wants to have sex with the person she's with, but just that the part of her brain that controls blood-flow to her vagina has decided that something to do with sex is going on and sex _might_ be about to happen.

The neural connections and parts of the brain that cause vaginal lubrication in a woman are very similar to the physiology and neural processes that cause a guy to get an erection. Virtually every guy will at some point in his life very much want to have sex, but not have an erection. And virtually every guy will have gone through a phase in his younger years when he got erections for no obvious reasons.

Similarly, women can experience vaginal lubrication when they're in a situation that's sexual, but which she doesn't find appealing at all. Rape is the most extreme example, but researchers have found that vaginal lubrication increases whenever a woman is shown a video with sexual content, even if she finds what she's seeing unappealing or even disturbing.

Given that your girlfriend spends her working day touching naked people (guys mainly, I assume), I don't find it surprising at all that there's evidence in her underwear at the end of the day that her vagina has been lubricating. It doesn't necessarily mean that she's found the men sexually appealing, and nor does it necessarily mean she's done something sexual with a guy, but just that the primitive, subconscious part of her brain that controls blood-flow to her vagina has been thinking, "Hey, this situation might lead to us having sex, so we better get ready for that."

As for her coming home horny, I suspect that's a little more complicated.

For some women, the sensations caused by increased blood-flow to their genitals can lead to conscious feelings of sexually arousal. It's sort of a tail-wagging-dog effect: rather than her finding a person and situation sexually arousing and this leading to vaginal lubrication, the increased warmth, feeling of heaviness and increased sensitivity of her genitals caused by heightened blood-flow leads her to consciously think, "Hey, I'm turned-on and I'd really like to have sex right now."

In your girlfriend's case, I wouldn't be at all surprised if she's sexually aroused by her getting guys off. After all, those guys are demonstrating in the clearest way possible that she's sexually desirable (and they're very likely telling her that as well), and most women find that very arousing.

There also a power-play dynamic that she might well find arousing. The guys have asked for something, she gets to decide if she wants to give it to them, they're under her control when she's jerking them off, and she decides when (and if) they're allowed to finish.