I know you must love them a lot.
That's what being a good mommy is all about. But to love is also to let go. Dogs also go through an independent stage. Once they grow out of puppyhood, they may have settled into a routine. It's great that your dogs have developed the confidence to not feel the need to be "clingy" or glued to your side. It's sad for us, I know. I have a fairly independent girl too.
It's not so much that she'd choose other humans over me, she's just more animal oriented first before 2 legged. Whereas, there are just some yorkies that are more people oriented than dogs and the "fun aunt" is just all a part of something "new" in their daily routine so it feels more exciting to them, probably.
I spend all of my time with my girl but when Daddy comes home, she gets more excited greeting him than if it had been anyone else... except when I disappear for hours too and then come back, I get greeted pretty much about the same way--the longer I disappear for, the sweeter the greeting.
Although when both her daddy and I disappear together while leaving her with family, she'd greet both of us happily, but probably obsess over her Daddy a little more.
Some yorkies are more attached to the hip of the owners than others. That's just a breed and an individual thing. Just keep loving them anyway and always be there for them. They'll know it and know you're their mom. Give it some time. Your Chelsea might eventually become your lap dog again or she might still stay as Little Miss Independent, but she's just as cute and sweet as ever, isn't she?
If you want more of a lap dog, I know my late Shih Tzu was a much better "lap dog" than my yorkie is though she also loved anyone and everyone so I'm sure she'd have happily gone home with anyone who lured her with food.