I *wish* I'd been in your shoes, since it was my breast, not the bottle that my LO refused! :( Because of that, I've been pumping now for almost 7 months, and I've done A LOT of reading on the subject. It is definitely true that the smell/taste of the milk changes when frozen (more or less depending on the amount of lipase in your milk). Our pediatrician advised us to mix bottles about 50/50 fresh/frozen so that LO doesn't refuse it because of the taste.
For your LO's age, I would try a medicine cup (you know - like what comes w/ the bottle of Robitussin) rather than a sippy and see if you can get her to drink that way. If that doesn't work, maybe try a syringe like what comes w/ baby medicine - it might be slow-going, but at least she'd get something in her. Oh - and you could also try freezing some milk in an ice cube tray and get one of those mesh feeders to put it in (sort of a teething ring thing that you can put food in a little attached mesh "baggie" so that it could melt through or be gnawed on, but no chunks could come through to choke). That'd be messy, but again - when you're desperate, it's good to have options!
Fortunately/unfortunately, it really does need to be someone else trying to give her the bottle/cup/whatever, and you probably need to be gone from the house. YOU are the milk wagon, and if she knows you're available, YOU are what she'll want.
One more thing about trying a bottle (if you have any energy left for that) - could the person giving it do so holding her in the exact position you use for nursing (the feeder should "hold" the bottle with their armpit and attempt to approximate the angle of your breast) and either wearing a shirt that smells like you, or at least have it sort of tucked around the bottle so that it's what the baby is smelling? I read somewhere (can't recall where now) that a LO who refused bottles was willing to take one in this way.
All that said, this weekend is coming SOON, and she may not acclimate to a new feeding method before you need to leave. Is there ANY way that you could bring her and a caretaker for her along so you could still nurse? It seems very stressful for all concerned to try to switch away from the breast in just a day or two, and if she feels too pressured, she might dig her heels in.
Oh, I thought of one other thing that would probably be a last-ditch effort. Is there another female around who you could ask to put your LO to her breast using a supplemental nursing system (aka "tube on the boob") so that LO is eating in a familiar manner? I know it's very unconventional, but again - when you're desperate, you need options!!
I would caution you against mixing your milk with formula, or if you do, to do so in very small quantities. This is because once you mix it, the mixture has the bacteria-promoting qualities of the formula and it must be consumed or thrown out in an hour (not even refrigerated - it really needs to be thrown out). I'd hate to see that liquid gold have to be thrown away!
Best wishes for you! I know it's hard, but keep up your inner smile, knowing that your LO is saying "there's no one as good as my mom!" :)