It sounds like you don't respect your girlfriend and while she is still interested in group sex you view it as an immoral thing, and it sounds like you think she's somehow "dirty" now.

Furthermore, whenever the subject of her sexual past is touched upon, a new detail usually ends up being revealed that causes me to become pensive, and she says I end up being cold to her for a while, though I am not really trying to be. For this reason we have agreed that it is now pretty much a taboo to speak about it. I have told her that I don't want to hear about it, and that I really don't like thinking about it. I just wonder if this is really only a band-aid solution.

It is, and it's not a real solution.

Also, I want to be there for her if this is some type of recovery period that she should be getting support during. It should be noted that I have personally slept with 8 different women in the 4 years that I've been sexually active - that's more than 4 times less in a period that is twice as long.

Does SHE actually feel like she needs to "recover" from anything?

Also, it's crazy to me how many guys judge women for sleeping with more people than they have slept with without thinking about the fact that sex basically grows on trees for attractive women. Women with a high sex drive who want sex could easily find new people to sleep with whenever they want to. That's just the fact.

I think if sex was so easy to come by for men and if men had this constant experience of people actually approaching them with their interest in sex (like a lot of attractive women do) they would also have a much higher partner count.

It seems to me like a lot of the time the only reason men have a lower partner count is because it's harder for them to just say "Hey want to have sex?" and get it.

Either way if you honestly think she's somehow immoral for having so much sex with so many people then you're obviously not compatible. It doesn't mean you're "wrong" but you clearly have different views about it. And unless she feels like she's wrong (which it doesn't sound like she does) and unless she feels like she needs to recover (from having so much sex, not from whatever emotional needs that weren't met that may have led her to having so much sex in the first place) then it sounds to me like this relationship could actually be damaging to her...because if she cares about you and you act like she's broken or dirty or morally bankrupt or whatever else then she's going to feel shitty about herself now.

To me when I was having casual sex I didn't have as many partners as she did but I still felt like having sex was like ordering a pizza, and I had casual sex with other people who felt the same way.

Serious meaningful sex is great but casual sex is a completely different thing.