I wouldn't leave her in the 29 for long, I have seen a DP kept in a 55 with two large commons Plecs... The plecs did not have fins, regardless that DP found a new home.
My recommendation is upgrade the two of them to a 10 gallon, increase the amount of plants and hiding places to break their line of sight. A 5 gallon is kinda small for them to not bump into each other.
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