What Should I Do If A Obsessive Female Follows My Boyfriend But Blocks me Is That a Red Flag?

So I'm this situation that a female follows my
Fiancé right and he told me that she's
just an old friend from high school because the
profile is kinda new she has a kid so she tries to follow me on social media and starts spying
around my page and all of the sudden she block me BUT STILL FOLLOWS him so I was like what the heck and I'm kinda concerned I don't know what are her intentions are I talk with my
Fiancé about this and he told me that it was really weird that she did that so last night he explained to me about their past
that she was crazy and has a crush on him ( telling him he’s cute etc ) Like SHE STILL DOES , she the type of girl that she won't stop till she gets it so besides that I told him to unfriend her because she's giving me red flags and I don't like her that she’s still flirting with
him on text ( like asking him it’s been so long if he’s single )
Since she block me I feel like she’s trying to ruin my relationship
What Should I Do If A Obsessive Female Follows My Boyfriend But Blocks me Is That a Red Flag?
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