Not terribly shocking as real estate agents who aren't salaried and get paid a % of the sale price are technically incentivesed to chase commissions, so unfortunately these situations do happen.
Bottom line, if you aren''t happy with your agent you have every right to move on. If you don't have a contract with this agent the only way he/she could try and keep the commission on this new deal is if they can prove what is called procuring cause via the Greater Boston Real Estate Board. Procuring cause is essentially a chain of events that leads to the sale of the property. If you have only seen this property with that agent, have no binding agency contract in place, and have not discussed pricing of the property/submitting an offer, your chances are pretty solid for not having to pay that agent after closing. Obviously there is always a small chance he/she (agent) could win an arbitration through the GBREB after you close on the property, but again if you break the chain of events early (now) and you have no binding agency contract in place those chances are VERY slim.
I don't suggest you make an offer on a property with out RE representation. That is simply because you should have someone who is protecting your interests in the deal by: helping you price the property (you don't want to over pay), being a great negotiator and helping you identify property faults, etc. This is a huge financial investment and having a professional that is making sure you are buying the right property for the right price is crucial.
Now that I have warned you, the answer is, yes, you can make an offer on your own. You can get a contract from the GBREB, fill it out and submit it to the sellers agent, or you could hire an attorney (warning: they are not real estate professionals). If you were to do any of the above, the sellers agent would keep the full 6% commission as the commission is a separate pre-negotiated contractual agreement between the seller and their agent and is essentially buried into your purchase price.
So, your options are: 1) Find a new buyers agent; 2) Find a new buyers agent who is salaried and gets paid a flat fee to avoid any chance of ill-motivations; Or 3) make an offer on your own or with the help of an attorney.
I hope that helps. Best of luck!