Find out what her hobby is and then say HI, I LOVE <her interest>! Since she's living with her mother rather than being Chad's fuck toy, the foid is probably severely autistic. It only cares about her interest, and anything that's an unknown is scary, including you. Speak slowly, clearly, in a monotone voice and praise her hobby. If you = her hobby rather than an unknown variable, she will want to spend more time with you.
Only speak about her hobby, and don't ask any unrelated questions. Then gradually make suggestions that will get her closer to your dick. Such as "HEY, CAN YOU SIT BESIDE ME SO I CAN HEAR YOU BETTER?". You're ugly so she'll say no you may think. Well no, since she will be considering the idea of sharing her interests more easily rather than being closer to your ugly face. See where Im going with this. Step 2 would be for her to sit on your lap. At that point she wont mind your hard cock touching her jeans, since that's unrelated to her interest. Continue this until you can start touching her cunt, making her suck your cock and then fucking her. Don't worry, it's not rape if she consents to doing you a favor so you can keep spending time with her.
Hence, you can cum inside this foid. But only if you handle her mother. If the mother is around a lot, you might have to actually have to speak to the mother for its approval for interacting with her daughter. Then you'll be fucked since you're an ugly fuck and the mother is NT. In other words you'll have to speak to your autistic neighbor only when the mother isn't around, and pretend to not be home every time the mother wants to get to know her daughter's new friend