Technically females can possibly get pregnant as early at 4 months, so yes, it is possible. But I'm not sure, the internet doesn't have a lot about when females can get preg; it might be 7 months earliest, in which case it's unlikely she's preg but possible. When did you adopt her? If she was with unneutered males any time after 4 months oop, it is possible. At 7 months oop, if she is pregnant then it's kinda concerning. Females aren't ready to be moms until about a year, and it's super risky on its own, PLUS without a father? It'll be rough, so I hope she isn't for your sake. Joeys will look like lumps. If it looks like chub, it is probably chub. Joeys are distinct lumps; give it a few weeks if it doesn't look more lump-like it probably isn't kids. But ya never know!