The elements of this crime can be found in California's Welfare and Institutions Code 15610.07 which states:
15610.07. "Abuse of an elder or a dependent adult" means either ofthe following:
(a) Physical abuse, neglect, financial abuse, abandonment,isolation, abduction, or other treatment with resulting physical harm or pain or mental suffering.
(b) The deprivation by a care custodian of goods or services that are necessary to avoid physical harm or mental suffering.
In California's Penal Code, this would come under PC 368. You can see the elements of the crime and the various penalties in the statute I have just linked you to. The charge can be a misdemeanor or a felony, depending upon the allegations of the complainant and the particular sub-section of the law being charged. The misdemeanor would have a maximum possible penalty of a year in jail. If prosecuted as a felony, there's a maximum possible penalty of 4 years in prison. There are also steep fines that could be involved and California, like all states, prosecutes elder abuse vigorously.
I understand that you are saying that the allegations are false, but the complainant has a different story, which is why you've been charged. Factual disputes as to what actually happened are what criminal cases are all about and which are resolved by a judge or jury after they hear all of the evidence. That means if you are not guilty of these allegations, you're going to have to fight this case.
There are many strategies that can be used to fight an elder abuse case. Which one works best depends on the specific facts and circumstances of your particular case. False accusations, for example, is a defense strategy in and of itself. Mistake would be another. Also whether the evidence shows any signs that the abuse occurred is still another. Some elderly people suffer from dementia or other forms of mental illness that distorts their perception.
So it's possible to fight a charge like this and even to win it. But you will absolutely need legal representation. I understand that lawyers can be expensive, but there are years of your personal liberty at stake here, and you need to entrust your defense to a professional. If you are indigent, you can plead not guilty on your court date and ask the judge to appoint you a public defender. If you have too much money and assets to qualify for a public defender, you will need to retain counsel. Many lawyers these days take credit cards, and that may be a solution for you.