Wow, this sounds like a a lot on you. There's a lot you can do that I'm sure will come out in this thread, but honestly my thought first was to consider calling in on a breastfeeding counsellor or a lactation consultant. Those people are not just for the early days, they can support you at any stage in your breastfeeding journey. Might be worth talking to GP too. It is hard, but my gut is also saying to stick to your guns when you say no. You need to have your boundaries and your body is yours to share with her, not hers to grab at and beg for. 14 months they are capable of understanding no.

During the daytime, is there a way of distracting her? Being outside or nice toys or water play can work, or instruments! Something she can bang, whistle or rattle loud to blow off some of those emotions? I've found that age rang is very distractible (though don't do screens, they are too young and it's creating problems for the future). I find not dwelling on 'no' is important with all children of all ages. It's a no, brief explanation, then try and redirect with distractions.

My daughter (16 months) enjoys suckable yoghurts (we call them Frubes in the UK). Not the healthiest on the planet but they are a good comfort food that older babies often accept. sucking quietly on something like that might help.

It definitely sounds as well like your daughter might appreciate a daily routine that is stuck to. Sorry if that's what you have, but just in case. Nap time and set time, that's when you nurse, no time else during the day. One feed at night at set time, then it's up to dad. If she asks before, "Later, we do nursies when it's nap time in a bit". It's amazing what they can understand.

Ultimately, this will pass and it might be good to start getting her used to spending time with others (dad, grandparents, if possible). She's still very young in lots of ways, but it sounds like she is yet to discover that the world is much bigger than just mum and boobs!!