You get the sense that Grandma was supposed to be a sort of come back film for Lily Tomlin. She plays the title character, a grandma who's an anti-social, out of work academic who was apparently a bad mother, but has been an okay grandmother. Julia Garner plays the granddaughter, she's a senior in high school who finds herself impregnated by her loser boyfriend; she's looking to have an abortion, but she needs grandma's help getting the money.
Grandma is plagued with many problems. The first being the ridiculousness of the premise. The entire thing hinges on the idea that neither Lily Tomlin nor Julia Garner can think of a better way of scoring 600 bucks than hitting up old friends and ex-lovers. Apparently they've never heard of instant approvals for credit cards online, Check-In-To-Cash, or getting a personal loan from a bank. Instead of doing something sensible, Grandma and her daughter go on a string of not-that-interesting visits to Grandma's old friends. These scenes are often riddled with sappy dialogue that none of the actors are able to sell, and they do nothing to further the plot, other than providing the characters with another dead end, to which Tomlin, of course, then remembers some other person she's burned earlier in her life that happens to owe her money. The movie goes on like this until ending with an uplifting note that just doesn't feel sincere, nor does it fit in with the rest of the film.
Over all, there are some scenes in which Tomlin shines (most of these you can see in the trailers), but they simply do not make up for the uneven tone, acting, and over the top premise.