My 13 month old niece doesn't like me?

My niece Madison turned 1 on Dec 16th. I'm married and we live with my sister Brandy her daughter Madison. I've been living with Madison since she was less than a month old. I've never had any kind of issues with her "not liking me" until recently.

She's an only child and her mom is very caring and affectionate. I've been very affectionate with Maddy as well, and my husband Matt is like her play-mate.

Recently Maddy has started to ignore me when I call her, and to slap my hands away when I try to pick her up. Sometimes when I look at her she makes this shrieking noise and turns away. This has been going on for about a week.

She still goes to my husband, and looks at him when he calls her name. The same with her Mom. It just seems to be me she's angry at.

Her life has always been very calm and she's been on a pretty strict schedule. Just this week my sister and I joined a gym and have been taking Maddy to the gym's daycare. She's getting better about being away from her mom, but her behavior towards me seems to coincide with this change in her schedule. This is the first time she's ever been in daycare, and she's only there for 45 minutes a day.

Help! Why doesn't she like me, or is this something I'm reading too much into? I'm upset, because she's very important to me!