Breastfeeding advice

Ni

Im nearly 23 weeks pregnant. Ive decided id like to breadtfeed this baby hopefully untill he's a year old. But i feel my mil is pressuring me into give him bottles so she can feed him. I have said i will express before we go to visit sometimes. I said I'm going to try and feed him untill he's 1 but shes like oh no thats to long we have to feed him. Obviously it will be ok to express just to give me a break occasionally but its like she wants him constantly on bottles. Shes even brought bottles and a sterillser for her house. Do i also need to only breastfeed for the first few weeks/months to get my milk flowing and stop him rejecting me after feeding from a bottle ? Even tho ive told my partner he wont be going for stay overs untill hes maybe 7-8 months old and starting solids( less reliant on my milk) they seem to think we will be leaving him with them after a few weeks. I know shes a first and only time grandma and very excited am i being selfish ? Please no hate I just want him to have best start but also want her to be involved as much as she can.