Weaning help!

I am returning to work in august and has been trying to wean her daytime feeds one at a time (i bf exclusively- no pumping) I just started with one of the feed last week but I am afraid that she is not getting enough food hence she has been waking up at night and I would need to feed her. I tried replacing the one skipped nursing session with formula but she doesnt like it that much and it takes 40 mins just to drink 60ml. I then offer her solids. I think she probably eats around 4-5oz.

The reason i dont pump is because my output is low hence I am replacing the feed with formula instead. I am still planning to bf when she wakes up and before bed time after I return to work.

So my question is, do I have to replace the missed feeding with formula? I am trying to add the feeding back in at a later time of the day instead and not sure if I should be doing that. I am juat assuming once she eats more solid she will just stop altogether.

Lost mama here :( would appreciate any help or suggestions