My little baby, Altaira, is four months old. I'm trying to socialize her, but she's just too shy with other dogs. I don't want to force her to interact with dogs and get a negative experience, but if I don't, then she'd never get a chance to familiarize herself with other dogs

I want Altaira to be more confident, but we don't have enough money for puppy parties and training classes so we just train her at home. When we go out on walks, she tires fast and I don't want to over-exercise her so I give her about fifteen minutes (especially in Summer, where her thick coat could overheat her) in two walks. There aren't a lot of dog owners in my area, so it's hard for her to see other dogs (much less young puppies her age).

I do have family members with dogs and I want her to visit them, but they have behavioral issues such as humping everything in sight, they're un-neutered, and territorial to what I know. I don't want Altaira seeing dogs like that; she could get harassed and might lash out at them in fear, not the mention the negative experience.

How could I make her a bit more assertive without means in the typical norms? Thank you.