@Brigitte Beauchat
You are dealing with multiple issues at a time. I'm not your lawyer and I'm not giving you legal advice, but let's try to take it step-by-step.
1. Motorcycles/Storage Issues. If this is an actual issue, then you can deal with it separately from the boyfriend question. If it's not a big deal, then it's not the root of the issue and you can move on.
2. "Unintentional" Tenant. I assume this is your biggest fear. Let's consider the extreme. There is another poster on BP who is currently dealing with a bizarre situation where a random squatter is living in his unit in Philadelphia. He is trying to figure out how to get him out (see the link below).
https://www.biggerpockets.com/forums/443/topics/47...
Stuff like that can happen even if you are the most careful landlord. So if you are absolutely terrified of the possibility of this boyfriend living in your unit for more than 14 days a month, then you can either have him sign the lease or decline to renew the lease with your current tenant.
3. What I would do. Again, this depends on the exact situation. But as a general rule, if I had a suspicion that my tenants are breaking some rule, I generally start with sending a letter --- by certified mail, return receipt requested --- reminding them about certain rules or lease terms. In some cases, I may expressly want to point out the facts that raised the suspicion. in other cases, I may draft the letter as a generic "reminder" letter to the tenant. In both cases, I would explain the underlying reasoning behind the rule and what the consequences are for the breach (i.e. eviction, fines, etc.).
The letter does two things. One, it reminds the tenants about the rules and that you as the landlord takes the rules seriously. Two, if there is ever a lawsuit between the parties, it can help you prove to the judge that you did not waive any rules or terms of the lease.
Now if there is a serious breach (e.g. tenant took a sledge hammer and started knocking down the walls for some reason), then obviously I'll act more urgently. But for other stuff, I may decide to be a bit more lenient about it and give the tenants to correct the issue on their own. For example, let's say the tenants have several kids and they are playing in the front yard. The lease says that they must not leave clutter in the front yard. Despite this, the kids leave the toy around in the front yard. If I just noticed it once, I may not do anything. If I notice a habit, I might send a generic "reminder" letter (seemingly addressed to all the tenants) that they need to clean up the yard. If that doesn't do it, then I slowly escalate the situation until it's appropriate. But I wouldn't start with the nuclear options (e.g. threatening to evict them unless they clean up the toys now).
If I was in your situation, I would've asked about the boyfriend and whether he was living there. If she answered "no, he just visits me twice a month" I would say that's fine and just remind her again that he will need to sign the lease if he starts to live in the unit for a longer period. I may include a written letter to that effect when you renew the new lease. And then I would see what happens and take it from there.
Obviously, consult with your own lawyer about this. But as a general rule, you can't really expect every tenant to follow your rules 100 percent of the time. It's just not realistic expectation whether you are dealing with rules for your tenants, rules for your own kids, or rules for your own employees. And I don't think you will sleep as a landlord if you treat every breach as a "high alert" situation.
I wouldn't see this particular situation --- based on the facts you wrote here --- as a "high alert" situation. Again, that's my own personal judgment and you may feel differently. You'll need to decide what's right for you.
4. Pennsylvania Landlord-Tenant Law. This is not directed to you, but I've been noticing many recent posters saying that Pennsylvania law favors tenants over landlords. Perhaps they are correct if they are talking about areas like Philly (for various reasons). But overall, I would say Pennsylvania law is pretty fair to the landlords. Notably, the law is fairly lenient when it comes to the kind of lease terms you can include to protect yourself as a landlord. So if you have some issue that you perceive as "unfair" to you as the landlord, try to find out what you can do to correct that issue. Many times, you'll find a decent solution.
5. Your lease. On last thought: I assume you are using the sample lease from the book that @Brandon Turner wrote. It's a great book and I consider it a required reading for all landlords regardless of their experience level. But I would be careful using that lease verbatim in Pennsylvania. Granted, I haven't looked at that form in a while, but I recall seeing some parts that clearly doesn't jive with Pennsylvania law. Also note that Pennsylvania law requires the landlord to use a residential lease that is written in plain language. Reasonable people could disagree, but I think it's a coin flip as to whether that particular lease could meet that standard.
Disclaimer: While I’m an attorney licensed to practice in PA, I’m not your attorney. What I wrote above does not create an attorney/client relationship between us. I wrote the above for informational purposes. Do not rely on it as legal advice. Always consult with your attorney before you rely on the above information.