I want to know a dua or zikir that can help my wife to start to solat n fall in love with Rasullah much more than i do.
The more you know about Sayyidina Muhammad (pbuh) the more she will love him. Teach her about his description, character, greatness and so forth. There are many books, and many articles online about these subjects.
Also, let her do a daily wird of 100-300 salawat upon the beloved Prophet (pbuh).
In terms of Duaa, she can use this duaa which Prophet (pbuh) used to make:
Allahumma inni asaluka hubbaka, wa hubbaman yuhibbuka,
Wal amal alladhi yuballighunee hubbaka,
Allahumma ja’al hubbaka a-habba illayya, min nafsi,
wa ahli, wal maa al-barrid.
”O Allah I ask You for Your Love and the love of those
whom You Love and the actions that will cause me to attain Your
Love. O Allah make Your love more beloved to me than myself, my
family and cold water. AMEEN
Success is from Allah,