While there is no single universal diet that works for everyone, I've dealt with a number of partial obstructions and a 2 full obstructions (both full obstructions were post-op). Google "Low Residue Diet" for some ideas on what is best to eat while your mother is recovering. There are even some sample full daily meal plans online you can use as a guideline. In general, soft, easy to digest foods are key. Skins and peels should be removed from fruits and vegetables, even if they are well cooked. Avoid high fibre/roughage foods such as raw veg, nuts, seeds, etc. Also, this goes without saying, but fluids are extremely important at this time. Blockages can result in dehydration, plus fluids are important in keeping BMs smooth and regular.
Some of my go-to foods when recovering from obstructions include scrambled eggs, pureed soup (butternut squash), mashed potatoes, smoothies, apple sauce, canned veg, smooth peanut butter, avocados, and oatmeal.
You can have Jello too, but I ate so much of that while I was in the hospital, I can no longer stomach it.
Best wishes to you!