Hi fpcs00, welcome to the boards! I'm glad you asked us about this.
""but does that mean she (P) never can have sex just because she's intellectually disabled?" I don't think that's right, it can't be"
- you're spot on that that's not right at all. Intellectually disabled people have a sexual self, a sexuality, and sexual feelings, as all people do. Intellectually disabled people have the same rights as everyone else to consensual sexual expression and consensual sex.
Many, many intellectually disabled people (some of whom I'm sure are reading along right now - hello, friends!) are
able to consent to sex, so it's definitely wrong to think that an intellectually disabled person couldn't consent simply because they're disabled. Sadly, though, it's very common that non-disabled people think intellectual disability = cannot consent, which may well be where your outspoken friend got that idea from. Unfortunately, the belief that intellectually disabled people cannot consent to sex is very ableist. It comes from non-disabled people's mistaken ideas and prejudices about disabled people, rather than from the actual lives and realities of disabled people.
It is true, of course, that a minority of intellectually disabled people cannot give meaningful consent to sex: if, for example, a person truly could not understand what they were doing, or had no way of communicating their wishes, or was unable to decline consent. (It's worth noting that those conditions also sometimes happen in various circumstances for non-disabled people, too!)
We can't meaningfully comment on whether your friend P could consent or not, because we don't know P and don't have P's input on what they wanted or how they felt. But:
P not always understanding what's going on doesn't mean they couldn't consent to sex: ability to consent to sex isn't determined by ability to grasp everything else in the world, only the ability to freely grasp and communicate about the sexual interaction with that person. Unless P has communicated that they were unhappy or confused or coerced or unable to communicate, there's no reason from what you said to think that there was any rape or abuse here.
It is worth my adding that yes, it is important for a partner or prospective partner to take care with consent, and make sure that the intellectually disabled person is able to interact and think in a way that suits the disabled person and not just the non-disabled person, because rates of abuse of intellectually disabled people are much higher than of the general population, for many reasons. Whoever a partner is, it's always important to only engage them in ways that they can understand, feel safe with, and can communicate about.
I'm not surprised that you couldn't find a good answer. While I was looking for further resources to link for you, I found little that is truly of use to intellectually disabled people: there was either a massive lack of anything about sexuality, or a small amount of information aimed at how to teach disabled people about consent. And, of course, there was a huge amount of really horrible, objectionable and misguided stuff on the general internet which left me feeling like I need brain bleach. I did find one thing I'd like to share with you, which you might also find helpful to share with your friendship group, if you and they both want it: https://www.mencap.org.uk/about-us/what ... t-we-think
Mencap is a UK charity for advice, support and advocacy for intellectually disabled people. The specifics of laws, for example, will be different in different countries, but I thought it might be helpful for you to see how they talk about this. For example:
What we want
We want people with a learning disability to be able to develop positive, informed, healthy and safe intimate or sexual relationships.
Does what I've said make sense to you? How are you doing with figuring out what you think about the tangle in your friendship group?
We're happy to talk with you further about any of this, if you'd like.