I am in a relationship with someone who remains in constant contact with her ex. Granted they have a child together, but I feel there is a stronger bond than just her involvement. Do I get over myself or walk away?

If they are co-parenting, their interaction is natural.

What does she say about it? Does she communicate with him openly in your presence? How often is it?

Do you think that you just have a hang-up about it? If so, you will likely drive her away eventually unless you get a grip. She has chosen to be with you not him. You might benefit from some therapy.

Best to get it straighten out before you go any farther. Parents will always have connections because of the children they produced. If you can’t accept that, stop now.

You’ve got a combo of strong forces working ‘against’ you. She clearly has to communicate with the ex for the child’s sake, and it sounds like she is also pals with the ex.
The communication regarding the child you should support and accept.
Some other recent question here asked about the complications of a partner who is friends with a lot of ex’s. That can be a challenge and seem threatening. If that’s the case for you, then at least talk it out with your partner and she how she responds.

How old is the child they have in common?

Are their discussions/interactions primarily about the child or are they about all kinds of things relating to each other (i.e. how was your work day, did you have a good sleep, what did you have for dinner, I need to buy a new couch)?

Get over yourself. This interaction is probably good for the child.

You should take this advice from OK Go.

I’m a divorced woman with children, remarried to a wonderful man. My ex and I are very effective co-parents, and are in frequent contact. I’m even in his house on a weekly basis, and used to be there daily. My second husband has absolutely no issue with this, which is just as it should be.