One of the standard definitions of "sexist" is discriminating against people based on their sex. You're very clearly discriminating here based on sex. So I don't think this is just my opinion. It might be just my opinion that this is a bad thing, even though, theoretically, I benefit by it.
The reason why I think it is a bad thing is that you limit your friendships to a subset of potential friends based on sex alone. Since you also place a qualifier of "aspie" here - and not many women/girls know when they are aspie compared to men/boys, you make your subset of a subset pretty tiny. Ie a fairly small number of women who may or may not be friendly.
And worse than that, you exclude a lot of potential male friends, who may well be more understanding than any woman could be. There's me being sexist. But when it comes to sex it is pretty hard for one sex to imagine (accurately) what it is like for the other.
And these potential male friends may well have sisters who are also aspie (whether they know it or not, it does run in families). So you miss out on a more reliable source of aspie women to make friends with. Ie for what ever reason you are being sexist, you potentially sabotage your own purpose.