How to invite your ex to lunch?

So we broke up in November, Haven't seen each other since December and limited contact since then. Last week we were catching up over text and she was asking what my chat was and how my family were etc. I just wanted to know the best way to invite her to lunch or something. What I want to stress to everyone is I don't have any intentions of trying to get back together with her, I only want to have a catch up with her because I want to have her in my life as a friend, we've always had fun together and I miss that.
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Sent her a text asking if she wanted to get lunch or something, she replied saying that would be nice. she just needs to check when she is working for a time when she is free.
How to invite your ex to lunch?
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