My advice - for what it's worth - would be: are you keeping notes, and are you studying carefully that which you have already covered? Because I might gently suggest that it would help you to take a pause and just recap the material to date before continuing on.
Latin is like a detective game (at least until it becomes a little more instinctive - as with most language-learning). There are numerous clues and it seems that you may be missing the significance of several, leading you - say - to match up whichever words are nearest to each other, rather than those which properly have Agreement: in Gender, in Number and/or in Case.
Look out for these 3 clues, which may not all apply in each/every sentence:
Gender: if the Subject Noun is Masculine, Feminine or Neutral, then is the describing Adjective also matching Masculine, Feminine or Neutral? (Agreement in Gender).
Number: if the Subject Noun is Singular or Plural, then is the describing Adjective matching Singular or Plural? (Agreement in Number).
Case: if the Noun is the Subject of the sentence, then it should be Nom. case, so is the describing Adjective also Nom. case, or is it Acc. case? In which case it is probably describing the Object instead. (Agreement in Case).
What about the Verb? What is it saying? Is it "visitat" or "visitant"? That will tell you who is visiting whom: the 'femina' or the 'discipulas'. But, as stated above, there are usually several clues for each scenario: if it was the 'discipulas' who were doing the 'visitant', then they wouldn't be discipulas in the first place - they would be discipulae. Like your favorite detective seeing the smoking gun in the hand of one of the dead people at the crime-scene: we see it, but we're not buying it. It don't look right. The subject noun has to be in the Nom. case, even if the verb seems to agree in number. Agreement in number but not in case is not enough agreement. But the verb was singular, so actually it rules out discipulas.
Latin has more Redundancy (spare clues) than -say - English, because it is highly Inflected (lots of different endings, or clues, that all matter).
Discipul-A is already enough to tell you it is a female student (cf. Discipulus).
Discipul-AE and discipul-AS tell you there are several female students.
Discipul-AE are Nom.case: they would be doing the visiting.
Discipul-AS are Acc. case: they ARE being visited.
There is a difference between the words NOSTRAS and NOS. :0
Nos is a Pronoun, like a Noun, it means: Us. But this clue is not present at this scenario, you should now be suspicious and check the other clues.
Nostras is an Adjective, a describing word. So what is it describing? It is describing something that is: a. Feminine (-A-), b. Plural (-AS), c. Acc. case - a Direct Object - (-S).
That works with discipulas, but not with femina, on 2 out of 3 check-details.
Femina means a Woman. It is a Noun, not an Adjective. It is therefore not describing anything: not even Discipulas. ;)
As we can see, that's a whole load of clues on offer. Any help?
Think about "discipulas nostras" as a single entity, noun + pos.pr. (with the pronoun after the noun, in this case). The same ending -as means acc.pl. here (the students are the object of the phrase) "Femina", nom.sg. (the subject of the phrase). If "discipula" were the "femina", it would have the same ending, I think.
I'd be in trouble had I not taken Latin in high school! I think all the newbies are extremely brave! Be sure to read and make notes (take pictures?1) of the Tips for every section, especially those Tables diagramming the nouns and verbs. Those differences are critical* Good luck!