It would be best not to open the snap that she sent you.
Yes, leaving her snap on open without answering it may give her the impression that you are ignoring her to some extent.
However, if you were to keep opening her snaps without answering, she may get the impression that you are playing a game with her.
This may actually make her upset.
She may decide to retaliate by ignoring you entirely.
If this happens, you would have given her the motivation to start ignoring you because she would believe that you are playing some kind of game with her.
This may defeat the purpose of getting her to start missing you.
An effective execution of the no contact rule is when you leave her constantly doubting herself about what is happening between the both of you.
If you make it too apparent that you are actually trying to ignore her, it may make you look weak in her eyes and she may start ignoring you as well just to spite you.
That is the danger of using a strategy of opening a snap but not answering it.
The no contact rule is not about you desperately trying to “show” her that you are ignoring her.
It is about you not acknowledging her in any capacity whatsoever.
Again, if you try too hard to “show” her that you are ignoring her, she may simply decide to return the favor out of spite.
This emotional response will not leave much room for her to start missing you.