In this array, 'mongst vulgars may'st thou roam.
In critic's hands, beware thou dost not come, (19-20)
“Vulgars” is an important word. It refers to the lower classes, to those that are poor (less educated, less well off financially, etc.). The book belongs among them, so says the speaker. It is too “poor” to hang out with those higher class critics.
And for thy mother, she alas is poor,
Which caused her thus to send thee out of door. (23-24)
Wait a second here, the speaker was angry earlier about having her poems stolen. Now, she’s saying she sold them for money? Hmm. Well, either way, sounds like she needed money and had to do something she didn’t really want to.