First of all know that she is acting normally for her age. It can be a tough age to be sure, I know, but what you are describing is totally age-appropriate. So perhaps when you feel the anger mounting take some breaths and remind yourself "she is 2 (not even!). This is normal. This will pass". Just to help yourself respond less emotionally, iykwim. Also remind yourself what you already know: you are staying away from home (trigger for "bad behaviour") and you are not eating as well as usual (trigger for "bad behaviour"). Remind yourself of this and it might help you to respond (in your mind) more gently.
Now, as for the behaviours....
Diaper changes can be hell at that age. I seriously don't know anyone IRL who has not gone through a difficult time with dipe changes when their kid was around that age. For pee dipes can you change her standing up? A lot of kids prefer a standing diaper change at that age. Obviously for poopy dipes you need to change her lying down. What I do with ds when he's fussy (which, btw, is waaay less often now that he's 2.5 yrs old) is lie him down in front of the tv and switch it on for the few mins that the d change takes. Try to think of other things that might distract her - I'm thinking let her hold an off-limits item like a cell phone for the time the d change takes?
Her saying "no" when you tell her not to do something... (can you give us some specific examples?)
One thing you can try to do is say "yes" as much as possible instead of "no". Try to see if you can "honour the impulse" behind what she's doing. So (for ex) if she's playing with her food, smearing it all around and making a huge mess you can re-direct her to an ok way that she can get the same sensory experience (playdough comes to mind). With a little creativity you can often come up with a way to redirect her from a "no" situation to a "yes" situation.
The other thing is to minimize the potential "no"s. Like if a problem is her running away from you in a public place then make sure you are holding her hand at all times, or keep her in a stroller or carrier. (At the same time take her to appropriate places to run around (park) when you can.) If lately she has been fussing when you take her to eat in a restaurant then for the time being switch to getting take-out (or food from the super market) and eat it in your hotel room or as a picnic at the park. Try to give some thought as to what might turn into a difficult (fussy, tantrummy, etc) situation with her and then just avoid it as best you can. Also, you're in a hotel room, so I know it's not as easy as when you're home, but try to put all "no" objects up out of her reach. Do your best to make her living space free for her to explore - ie. a "yes" zone.
Good luck mama - I know it isn't easy!
