I'm so sorry to hear that Annabelle has lymphoma. I lost Baron (avatar photo) a few months ago to a very rare and virulent form of lymphoma, called hepatocytotropic lymphoma, that killed him in just 8 weeks, even with no holds barred treatment. From what you described though it sounds like Annabelle has the common variety of lymphoma which isn't as aggressive and responds better to treatment, meaning that she can likely have a decent quality of life for six months to a year.
Generally, the treatment consists of steroids plus some variety of what's called the CHOP protocol. CHOP is an acronym for the four chemo drugs that they use. There is also another drug called L-asparaginase that can be used as a rescue or emergency drug to temporarily set the cancer back (on the first use it kills 99%+ of the cancer cells, but each repeated use is less effective, as the survivors of the previous use(s) become increasingly immune). Additionally, if money is no object there are some alternative treatments that involve bone marrow transplants or T-Cell reprogramming (akin to what is being done at the forefront of lymphoma treatment for humans), which are available in a few places in the country.
I was trying to get one of those alternative treatments for Baron as I felt that was his only chance given what I was told about how virulent his variety of lymphoma was, but I found out that they also require the patient to be in "molecular remission" prior to attempting these treatments, which means that in addition to being in clinical remission (i.e. no symptoms) there can be no detectable cancer cells or DNA from cancer cells in the blood. Baron was only in clinical remission for 4 weeks before the cancer he had overwhelmed all the chemo he was getting and caused his liver to fail; so I wasn't able to get the requisite DNA testing done on the cancer cells, or get the logistics of transporting him to Seattle for additional testing and possible treatment finalized, before his time ran out.
If you want to private message me I can give you more details about the treatment options and side effects.