How should I proceed with my landlord situation?

My landlord asked if we would mow the lawn, and when we asked if we could get a rent break for doing it, she freaked out, stating that she was going to raise the rent or kick our third roommate out. Only myself and my husband are officially on the lease, but we know from Burlington, Vermont law (where we live) that our roommate is a legal tenant anyways, so she can't just kick her out. We also know from Burlington law that she needs to give us 90 days written notice in order to raise our rent. The problem is is that she is unreasonable, and if we don't give in to her demand to start paying an extra $100 by August first (which she has asked for by text message, not in written notice, and gave us less than 60 days notice for) and instead request formal written notice, I am 100% positive that when she does give us written notice, it will be to raise the rent by at least $300, if not more. We signed an 18 month lease with her, which doesn't end until April, and had heard from our local tenant's association that we can't be held to a lease of more than 12 months unless it's been registered with the clerk's office, which it hasn't been. Unfortunately, the tenant's association hasn't been able to find this statute, and when I spoke to a local lawyer, he didn't know anything about it either. He suggested that we just give her notice anyways, break the lease, and let her take us to court. If we can't leave legally until April, what should we do? If we try to fight back and insist on notice, we could be stuck dealing with substantially higher rent and her wrath for almost 10 more months. Advice?