It depends. If the portrayal of the yandere girlfriend is done in an interesting and nuanced way, it could be appealing. But if it's overly stereotypical or one-dimensional, then no.
Most real - life 'yandere girlfriend' stories are not as extreme. Often, what seems like yandere behavior can be a result of insecurities. A girl may have had bad experiences in past relationships or might have self - esteem issues. So, she acts overly protective or jealous. However, it's not the same as the full - blown, often dangerous yandere concept from fictional works.
Communication is key. Sit down and talk to her about how her behavior makes you feel. Let her know that her excessive jealousy or possessiveness is not healthy for the relationship.
The ending of Girlfriend Girlfriend manga is quite complex and bittersweet. The characters go through various challenges and their relationships evolve in unexpected ways.