The plaintiff has shown incredible dedication and compassion by caring for her FIL for a decade, even after her husband's passing. She made her intentions clear from the beginning of the relationship. It is unreasonable for the boyfriend to now demand she abandon her commitment and betray the trust of her FIL. He knew from the get-go what the situation was.
The plaintiff is being unrealistic and selfish by refusing to consider the boyfriend's feelings and future. She is prioritizing her FIL's needs over her partner's, creating an unbalanced relationship. Her refusal to even discuss alternative care options shows a lack of consideration for her boyfriend's concerns about their shared future and potential burdens. She's basically dooming the relationship.
The plaintiff has the right to care for her FIL, especially given her long-term commitment. However, she should have been more open to discussing the boyfriend's concerns and exploring potential solutions that could accommodate both their needs. The boyfriend is not inherently wrong for voicing his worries about the long-term impact of this arrangement on their relationship, but his approach lacked sensitivity and understanding. A compromise should have been attempted before resorting to ultimatums. Ultimately, the boyfriend is being unreasonable in demanding that she abandon her FIL. However, her stubbornness in not considering other options is causing a lot of unnecessary friction.