How do you ween a baby form breastfeeding????

I have a 10 month baby who i am currently breastfeeding. She is my third child and i have breastfeed all of my children. But for some reason i am not able to ween this one form the boob. the longest i breastfeed my other two was 6 month and 8 months and they took to the bottle with no problem. but for some reason my 10 month is not interested in the bottle (i have been trying since she was 8 months) then i thought about giving her the sippy cup with soft spouts but she thinks this is a toy. i breastfeed her in the morning after her breakfast then i can go all day not feeding her the boob just offering her the cup but all she does is play with it and does not get all the liquid i think she should be getting. then i feel bad that she has not had enough to drink and i end up breastfeeding her before bedtime. i am due to go back to work in May and my time is running out. what do i do how do i break her form the breast? I do love the bonding experience that we share during the breastfeeding time but i do have to go back to work and i do think she is getting too old to still breastfeed. if there is anyone out there that has been through this problem and you have a answer for me please tell me. thank you