How to keep a temporary long distance relationship going?

Me (M 27) her (F 32) both live in North Carolina so my girlfriend has a son (not with me dad not in picture) who has medical health issues and the best place to treat these issues is in California she has been in California since April with her mom and son. Before she left I asked for her parents blessings and I proposed to her she said yes she most likely won’t be back until September. How do you keep the spark alive? I’m not going anywhere never would there is a reason I proposed. But how do I trust her that everything is good between us and how do I trust her when times get hard in the distance that she will stick it through and come back home to me when everything is good. How do I keep the love going and her not to fall out of love for good. I understand she has a lot going on not being inconsiderate but I’m so fearful she will lose the love and not come home to me and us
How to keep a temporary long distance relationship going?
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