Yeah, how old is she? And you really need to get informed about these drugs. Skipping doses can cause withdrawal, although this is less likely with Prozac than other ssris because it stays in the body much longer. When someone skips a dose, you just take the next dose -- doubling up can cause side effects. Prozac is one of the more stimulating ssris, and these drugs can cause odd thoughts especially in the young. Marijuana is a no no for most people with anxiety problems -- it tends to bring it out, though for some it is relaxing but not for most. Many have their first anxiety attacks on pot. Many on this forum did. I don't know why she was in the ER for two days from getting paranoid on pot, that's common, so I'm guessing it was the combination of the overdose of Prozac. If you take too much of an ssri you can get something called serotonin syndrome. And if she's going through mood changes, that's not anxiety, that could be something more complex, such as bipolar. Is she seeing a psychiatrist or a regular doc? Is she really going through mood changes and paranoia, or something more mild than that description? Here's the thing I've learned after years of this -- you need to do your homework. You can't rely on doctors to have done theirs.
What side effects are you referring to other than tiredness? After 4 months I imagine any remaining side effects will not go away without a change of med. Hard for you to figure if she really is tired, since it is often hard for the user to determine what is a new physical situation and what was just ignored previously.
How old is she? Are you watching her take the dosages now?
When she was on 20 for 2 weeks and none some days, I wouldn't give her 40s immediately, fyi.