My son, age 17, is on Spectrum. My daughter, age 13, is not.

The key is to set aside time every day that is dedicated just to your daughter.

Parents unsure about having their kids over to your house for her? Have a larger get-together for her (find some excuse - a favorite minor holiday, a welcome-spring barbeque, or something), with someone designated to keep your son very busy, and have the PARENTS (and your daughter's friends) over to get to know you and your daughter better.

By the time, close to the end of your party, when your son wafts in for the food or whatever, the other parents will know you well enough not to make a first judgement based on him.

your local disability resource center might have "sib-shops" workshops for siblings of kids with special needs. A place where their are other kids like them to talk about the issues and be encouraged to be honest about their own feelings...

It depends on the child. Some children might see it as unfair while others will merely understand, and deal with it the best they can. Being the older sibling (even if only by three years) it might have been a bit easier for me to understand, but I never was one to constantly be upset by something like that since I believe my mom loved me just as much since was infact my mom. (Though, yes, there were times were I'd wonder why she couldn't spare time with me, but that's natural.)
Your daughter sounds a lot like how I go about dealing with a sibling who's within the spectrum. Childer are very smart and can understand situations if they are explained properly. If she hasn't asked "Why don't you pay attention to me too" then it might be that she simply understands that her brother is different, and might need more attention and taking care of, while still knowing you love her just as much. I'm sure if you ask her about how she feels she'll tell you about it, but even if she doesn't ask for anything talk to her friends parents and see if there is a chance some of them are willing to let their child over instead of just assuming they won't. - Daughter

My son with Autism is 13 and my daughter is 17. It was really difficult for her. You need to hear it from the child's perspective. If you want my daughter to answer let me know.

I had a hard time juggling time for my NT son who is 20 months older than my son with Autism. I did the best I could.

But I did let my NT son have friends over A LOT! Because I wanted him to have normal interactions with kids and because he loves having someone to play with. I just got to know the parents when he was younger.

Since I did not have time to get to know several parents we just stuck with 3 or 4 of the closest friends. It was not hard to strike up a conversation about the kids during the drop-off or pick-up... I'd ask them questions about the friend and the other kids in the family. Then I let them know about mine. The parents were all very supportive.

Since my autistic son couldn't handle the noise and I wanted the kids to play independently, I normally limited it to one or two kids at once. We did a ton of sleepovers.

I also made it clear to both my NT son and his friends that I would not tolerate them making fun or calling names. I only had a problem once and it was easily handled.

My NT son is very loyal so his closest friends pretty much stayed the same. I got to know their parents well over the years... and we have supported each other as parents. In a way, we sort-of group-parented. I highly encourage you to look for a parent(s) like this. It was so helpful to have others looking out for my son while I looked out for theirs. Especially in the teen years.