You appear to be reading from the script of 'Little Women'. However, the script reads: I don't know. You see, my Aunt March has rheumatism, and her doctor thought that the baths. Oh, not that she hasn't a bath. She has a very nice one. In this case, there is a difference between "the baths" and "bath". A bathtub is something that people wash themselves in. "The baths" is a colloquial term that means "the bathhouses". These are places where anyone can go to have a bath. Usually, this means with other people. The Aunt has an illness, and the doctor has suggested that going to a bathhouse would be a good way to treat the illness. Resting in hot water can be good for muscles. However, the speaker notes that the Aunt has a bath of her own - so it's a little weird that the doctor has recommended going to a bathhouse. Looking at the larger conversation, the characters are talking about life in Europe compared to in America. At that point in time, Europe had a lot of things that would be considered strange or interesting to an American, and they are commenting on this.

bath as in the tub where you take a bath/shower. The sentence means her aunt has a joint disease where taking baths is good treatment. The doctor or she thinks taking baths in Europe are good, which is why she mentions this. Her aunt does have a bath at her house, so she doesn't need to go to Europe to take a bath, she is just asking/having random conversation.

There's nothing complicated here - 'baths' just refers to the practice of taking a bath. The sentence isn't finished, though. It probably continues something like this: "My Aunt March has rheumatism, and the doctor thought that [taking] baths [ would help relieve the pain]. The section "Well, not that she hasn't got a bath. She has a very nice bath" is a rather silly side comment. It's a kind of word play on the ambiguous phrase 'have a bath'. 'Have a bath' has two meanings. It can mean 'take a bath' (as in immerse yourself in water), which is what the doctor meant. The speaker is making a weak joke by commenting that the aunt 'has got a bath', which is the other interpretation of the phrase 'have a bath' - meaning that she possesses a bathtub. By the way, you can't say 'What does the sentence meaning?'. It should be 'What does this sentence mean?' if you want to use the verb 'mean', or you can say 'What is the meaning of this sentence?' if you want to use the noun 'the meaning'.