Worried about Dehydration

My mom is stage II Her2+. Her first round of chemo was 2 weeks ago today, and she is have a horrible time with side effects. She's had diarrhea since then (even with a prescription), and now she's beginning to have dry heaves. She's becoming dehydrated and is going in again today for a liter of fluid to be put into her (her 3rd time in the last week). She knows she needs to drink and eat, but is having a very hard time doing this. I'm trying to support her and encourage her to drink (bought her water, Gatorade, propel, etc.) but she's not able to drink any of it. She's become very weak and I'm worried that she's giving up (she continuously tells me how much of a whimp she is, and I'm trying to convince her she's not).

Does anyone have any advice on how to get my mom to drink more liquids (we've tried jello & Popsicles too with no success) or consume more food without being pushy? Also, I'm trying to be very positive but I feel as if she's not in the positive mind set, any advice on how to get her to become more positive & take on that warrior mindset?

Thanks!!!