I know people have strong feelings about flashbacks. Here's my issue-- My main character is a teenager (at first) who is in her own head a lot, as most teens are. She thinks about people she's known in the past and how they changed her in the way she relates to people she knows now. She is confused by boys, etc. and her train of thought goes to other interactions she's had with boyfriends. Obviously, that 'thinking' is a flashback. Memories are flashbacks, right? I think some personalities live in the past a lot. I know I do it. I am constantly assessing people or situations based on previous ones...and it comes out on the page. In addition, this girl, my main character, has a grandma who loves to tell stories about when she was a young girl first coming to this country. They are funny, sad, and usually very meaningful to the MC. Again, are these stories considered flashbacks? They are truly necessary to my story, and *I* think they are interesting in the way they tie things together.
I don't see why you couldn't ? Flashbacks can be very useful . And I think that it depends on the way you write it , if you use your MC , saying her grandma told her that and that... I don't think it could be a flashback, but if it's the grandma talking, it could be .
I also think flashbacks are incredibly helpful to bring a story together. This is a great way for the reader to know your character, what got her to where she is and why she thinks a certain way about things. The only thing I would suggest is not have her live in the past too much (Although her character does), only so your story is constantly moving forward. And Grandma telling stories is just that, I wouldn't consider it a flashback, only because it doesn't belong to your MC, unless, she is remembering all those stories of hers, then, it is indeed a flashback and I don't see why it would be a problem unless it becomes repetitive. Good luck!