Had not had a dog in heat for, gosh, I don't know how many years until Mardi joined us. Yep, within a few days she came into heat. It really was not all that bad. We have a large kitchen/eating area with a tile floor so she spend most of her time in there. She was crated at night. She would not tolerate any panties at all.
We had Bandit at the time, who was neutered, and he was interested in her so they were kept separate or monitored. Mardi was a complete hussy!
Yes, at least 28 days keep her under house arrest. Remember, the last week she is the most fertile. You will need to let her finish the heat and wait 2-3 months before spaying, if you plan to do it this early. You need to give the area, which is very blood rich at this time, time to get back to normal.
If you do board her she might be ready but I would take precautions at least by letting them know. Her next heat cycle might be in 6 months. This often depends on what her mother's heat cycles were like. I have heard about dogs coming into heat at her age so don't think it is that much out of the norm.
In the evenings, with Mardi, we would allow her in the living room in the evening after we covered it with cotton blankets which were easily washable. She will bleed more at first and then it will slow down but don't be fooled, you need to protect her for the full time, 28 days.