It's not an easy situation. The truth is that your daughter is doing what is perfectly normal--she is bonding with her primary care-giver and that happens to be your helper. When your mom was around your mom was spending a lot of time with her too and she bonded with your mom. That shows that your daughter will bond easier with people who spend large amounts of quality time with her and care for her. This gives you hope--there is nothing really "special" about your helper--she just reaps the rewards of extra attention and bonding because she is there to put in the hours of "face-time" with your daughter. This is just how it goes.
At 14-months-old, "catching up" in the mornings or at night "if she's awake" probably won't be enough to "make her understand" that you care about her. The only way to do it is to put in the time. Children are wired and designed to bond with the people they spend most time with--not just the people they are biologically related to. That's how I see it. It doesn't mean you're less important but she is closer with your helper simply because of the time invested. This is where we all have to make hard choices in life and hope that things will turn out okay--sometimes it really is impossible to "have it all" without one area having to suffer some or a lot. It could be a phase but it's too early to say, I think.
But, my daughter is now 15-months-old and doesn't have this issue even though I'm working full-time. But, I don't work until super late at night and she sees me during my lunchbreaks every day and I am with her all day on Saturday and Sunday. It's also individual to the child. I'm also still breastfeeding her several times/day and I credit this for increasing our bond.