Small female lapdog (Killeen, Tx)

Last Christmas I found a small black female dog wandering around my apartments, I took her in because it was freezing outside.
I got her checked for a microchip and posted many found dog signs, but never found the owners.
It’s been almost a year, but I really can’t keep her.
I believe she is either a dachshund and chihuahua mix, or a dachshund and miniature pincher mixed.
She has stranger danger when you first meet her, but after a couple of hours she warms up to you.
She can pee on a pee pad, but to poop she needs to be let outside.
She prefers going potty outside.
She would be a good lap dog, or companion.
I can’t have dogs at my apartment, so I been keeping her at my parents house so she is use to my sister who’s 10, and she’s been around cats, ponies and a bunny.
My parents have chihuahuas that bully her though, so I am trying to find her a loving home.