Introducing bottle

Nikki
Hi! 
My 7week old is EBF. I go back to work in 3 weeks and have started to introduce a bottle of breastmilk.. But she will not latch! She will let it in her mouth, but she gums it and spits it out and will cry until she gets the real thing. 
I'm so nervous about going back to work if she still isn't taking a bottle. The thought of her crying for me all day breaks my heart. 
The lactation consultant said to keep trying with the same bottle and that all bottles are essentially the same and won't take one over the other.. But I've heard differently. 
Any momma's out there have any experience with this?? Did your baby refuse one bottle but take another?