The second sentence expresses the speaker's opinion, it suggests an annoyance or irritability at the frequency with which the woman is seeing non-existent things. The present progressive tense is used when we mention the activity, and with many senses we can use this structure.
A: What are you doing?
B: I'm tasting this stew. I think it needs a bit more salt. What do you think?
A: Where's he going?
B: He's seeing his new girlfriend. (In this instance see = meet)
A: Why is he always touching his hair like that?
B: Because he's either incredibly vain or terribly insecure. Your pick.
A: Why are you smelling that meat? You only bought it yesterday.
B: I'm sure it's gone off. Here, have a sniff.
A: We're hearing all sorts of awful stories about the new neighbours.
B: It's just idle gossip, they're perfectly fine people.
Now is the present simple tense and the progressive tense always interchangeable? No, it isn't. Compare:
A: What do you do?
B: I taste wine for a living.
A: What are you looking for?
B: My glasses. I can't see a thing without them.
A: If I told you once, I told you a hundred million times. Don't touch the DVDs with your grubby fingers.
A: They say dogs can smell cancer.
B: Really? I never knew.
A: Can you hear it? There's a noise downstairs.
B: It's nothing. Now go back to sleep.
John Lawler in an answer posted a succinct explanation on volitional and non-volitional verbs
Hearing: You listen to something on purpose, but you can hear it by accident.
Vision: You look at something on purpose, but you can see it by accident.
Verbs for the other three senses don't vary; you can smell, taste, or touch/feel on purpose or not.
Therefore with non-volitional senses such as sight and hearing, we often use can and the verb remains in the present simple, the progressive tense is more common with things we do on purpose.
Without going into greater detail, I find that Wikipedia explains well some of the differences between the present simple and continuous
Verbs of mental state, sense perception and similar (know, believe, want, think, see, hear, need, etc.) are generally used without progressive aspect, although some of them can be used in the progressive to imply an ongoing, often temporary situation (I am feeling lonely), or an activity (I am thinking about a problem). See also can
The present progressive or present continuous form combines
present tense with progressive aspect. It thus refers to an action or event conceived of as having limited duration, taking place at the
present time. It consists of a form of the simple present of be
together with the present participle of the main verb.
We are cooking the dinner now. This often contrasts with the
simple present, which expresses repeated or habitual action (We cook dinner every day). However sometimes the present continuous is used with always, generally to express annoyance about a
habitual action:(emphasis mine)
- You are always making a mess in the study.
Certain stative verbs do not use the progressive aspect, so the
present simple is used instead in those cases