How I felt about it. Vagabond pulls a Sunset Blvd. in its opening scene. The protagonist is dead. The rest of the film is a flashback that finally leads to the inevitable, the corpse at the side of the road. The mystery, then, isn't what happens to her, but how she gets there.
The short answer is, she does it to herself. Bad judgment foils numerous chances at redemption, until the cold of winter and a short string of bad luck does her in.
Many take an interest in the young and potentially attractive drifter. Some, of course, want her for sex. These men range from a stalker who rapes her in a forest, to a farm laborer who hungers for her but never lays a hand on her. Other men she understands, those who use her for sex while she uses them for alcohol, pot, food, or shelter. Sex with a young man is fine as long as the good times last. She bolts at the first sign of trouble.
We gradually understand Mona's character. She works only when she has to, and dislikes it. She also has no understanding of what role is being asked to play, aside from that of short-term lover. Two different forty-something women take an interest in her. One is simply lonely, the other is a professor and probably plans to write a paper on her.
For such people, Mona is a novelty. They recognize she is from a middle-class family, but couldn't take the structure required of an adult life in society. They feel sorry for her, but are unwilling to take her in. Such an act would be as irresponsible as Mona herself.
Mona's best chance at redemption is at a goat farm. She makes a deal with the sympathetic family: plant a small section of land, and help with goat cheese and milk production. In return, she will have shelter, space, and stability. But Mona can't keep up her end of the bargain. She is just too lazy and indiscreet.
How others will see it. For once, the French subtitles aren't likely to dissuade American viewers. This is not a dialogue-intensive film. Many viewers will be fascinated by Mona. Like the characters she comes across, they will find different potentials in her. But whatever they expect from her, they will be as disappointed as the people she meets on the road.
Would anyone care about Mona if she were unattractive? The goat farmer family probably would. They judge by character instead of appearances. But most of the other people she meets would avoid her if she were homely.
A final question: is Mona mentally ill? She has little sense of the future, or of decorum. She ought to know better. But she's sane. If she's different from you and me, it's because of her philosophy: comfort now, or I'm leaving.